Silence missing unlock from Coverity.

Save 'i' to 'locknum' and use that rather than using 'header->node->locknum' when performing the deferred unlock as 'header->node->locknum' can theoretically be different to 'i'.

8072static isc_result_t
8073getsigningtime(dns_db_t *db, dns_rdataset_t *rdataset, dns_name_t *foundname) {
8074        dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
8075        rdatasetheader_t *header = NULL, *this;
8076        unsigned int i;
8077        isc_result_t result = ISC_R_NOTFOUND;
8078        unsigned int locknum;
8079
    	1. Condition rbtdb != NULL, taking true branch.
    	2. Condition rbtdb->common.impmagic == (1380074548U /* (((0x52 << 24) | (0x42 << 16)) | (0x44 << 8)) | 0x34 */), taking true branch.
    	3. Condition !!(rbtdb != NULL && rbtdb->common.impmagic == (1380074548U /* (((0x52 << 24) | (0x42 << 16)) | (0x44 << 8)) | 0x34 */)), taking true branch.
8080        REQUIRE(VALID_RBTDB(rbtdb));
8081
    	4. Condition !!(isc_rwlock_lock(&rbtdb->tree_lock, isc_rwlocktype_read) == 0), taking true branch.
    	5. Condition !!(isc_rwlock_lock(&rbtdb->tree_lock, isc_rwlocktype_read) == 0), taking true branch.
8082        RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
8083
    	6. Condition i < rbtdb->node_lock_count, taking true branch.
    	13. Condition i < rbtdb->node_lock_count, taking true branch.
    	20. Condition i < rbtdb->node_lock_count, taking true branch.
    	28. Condition i < rbtdb->node_lock_count, taking true branch.
    	38. Condition i < rbtdb->node_lock_count, taking false branch.
8084        for (i = 0; i < rbtdb->node_lock_count; i++) {
    	7. Condition !!(isc_rwlock_lock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	8. Condition !!(isc_rwlock_lock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	14. Condition !!(isc_rwlock_lock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	15. Condition !!(isc_rwlock_lock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	21. lock: isc_rwlock_lock locks rbtdb->node_locks[i].lock.rwlock. [show details]
    	22. Condition !!(isc_rwlock_lock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	23. Condition !!(isc_rwlock_lock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	29. Condition !!(isc_rwlock_lock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	30. Condition !!(isc_rwlock_lock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
8085                NODE_LOCK(&rbtdb->node_locks[i].lock, isc_rwlocktype_read);
8086                this = isc_heap_element(rbtdb->heaps[i], 1);
    	9. Condition this == NULL, taking true branch.
    	16. Condition this == NULL, taking true branch.
    	24. Condition this == NULL, taking false branch.
    	31. Condition this == NULL, taking false branch.
8087                if (this == NULL) {
    	10. Condition !!(isc_rwlock_unlock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	11. Condition !!(isc_rwlock_unlock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	17. Condition !!(isc_rwlock_unlock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
    	18. Condition !!(isc_rwlock_unlock(&rbtdb->node_locks[i].lock, isc_rwlocktype_read) == 0), taking true branch.
8088                        NODE_UNLOCK(&rbtdb->node_locks[i].lock,
8089                                    isc_rwlocktype_read);
    	12. Continuing loop.
    	19. Continuing loop.
8090                        continue;
8091                }
    	25. Condition header == NULL, taking true branch.
    	32. Condition header == NULL, taking false branch.
8092                if (header == NULL) {
8093                        header = this;
    	26. Falling through to end of if statement.
    	33. Condition resign_sooner(this, header), taking true branch.
8094                } else if (resign_sooner(this, header)) {
8095                        locknum = header->node->locknum;
    	34. Condition !!(isc_rwlock_unlock(&rbtdb->node_locks[locknum].lock, isc_rwlocktype_read) == 0), taking true branch.
    	35. Condition !!(isc_rwlock_unlock(&rbtdb->node_locks[locknum].lock, isc_rwlocktype_read) == 0), taking true branch.
8096                        NODE_UNLOCK(&rbtdb->node_locks[locknum].lock,
8097                                    isc_rwlocktype_read);
8098                        header = this;
    	36. Falling through to end of if statement.
8099                } else {
8100                        NODE_UNLOCK(&rbtdb->node_locks[i].lock,
8101                                    isc_rwlocktype_read);
8102                }
    	27. Jumping back to the beginning of the loop.
    	37. Jumping back to the beginning of the loop.
8103        }
8104
    	39. Condition header == NULL, taking false branch.
8105        if (header == NULL) {
8106                goto unlock;
8107        }
8108
8109        bind_rdataset(rbtdb, header->node, header, 0, rdataset);
8110
    	40. Condition foundname != NULL, taking true branch.
8111        if (foundname != NULL) {
8112                dns_rbt_fullnamefromnode(header->node, foundname);
8113        }
8114
    	41. Condition !!(isc_rwlock_unlock(&rbtdb->node_locks[header->node->locknum].lock, isc_rwlocktype_read) == 0), taking true branch.
    	42. Condition !!(isc_rwlock_unlock(&rbtdb->node_locks[header->node->locknum].lock, isc_rwlocktype_read) == 0), taking true branch.
8115        NODE_UNLOCK(&rbtdb->node_locks[header->node->locknum].lock,
8116                    isc_rwlocktype_read);
8117
8118        result = ISC_R_SUCCESS;
8119
8120unlock:
    	43. Condition !!(isc_rwlock_unlock(&rbtdb->tree_lock, isc_rwlocktype_read) == 0), taking true branch.
    	44. Condition !!(isc_rwlock_unlock(&rbtdb->tree_lock, isc_rwlocktype_read) == 0), taking true branch.
8121        RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
8122
    	
CID 288552 (#1 of 1): Missing unlock (LOCK)
45. missing_unlock: Returning without unlocking rbtdb->node_locks[i].lock.rwlock.
8123        return (result);
8124}