CID 351370 & CID 351371 after ADB refactoring

@each results of ADB refactoring?

*** CID 351370:  Program hangs  (LOCK)
/lib/dns/adb.c: 2699 in dns_adb_cancelfind()
2693     
2694     	LOCK(&nbucket->lock);
2695     	ISC_LIST_UNLINK(adbname->finds, find, plink);
2696     	UNLOCK(&nbucket->lock);
2697     
2698     cleanup:
>>>     CID 351370:  Program hangs  (LOCK)
>>>     "pthread_mutex_lock" locks "find->lock" while it is locked.
2699     	LOCK(&find->lock);
2700     	if (!FIND_EVENTSENT(find)) {
2701     		ev = &find->event;
2702     		task = ev->ev_sender;
2703     		ev->ev_sender = find;
2704     		ev->ev_type = DNS_EVENT_ADBCANCELED;

*** CID 351371:  Null pointer dereferences  (REVERSE_INULL)
/lib/dns/adb.c: 2615 in dns_adb_createfind()
2609     	/*
2610     	 * Copy out error flags from the name structure into the find.
2611     	 */
2612     	find->result_v4 = find_err_map[adbname->fetch_err];
2613     	find->result_v6 = find_err_map[adbname->fetch6_err];
2614     
>>>     CID 351371:  Null pointer dereferences  (REVERSE_INULL)
>>>     Null-checking "find" suggests that it may be null, but it has already been dereferenced on all paths leading to the check.
2615     	if (find != NULL) {
2616     		if (want_event) {
2617     			INSIST((find->flags & DNS_ADBFIND_ADDRESSMASK) != 0);
2618     			isc_task_attach(task, &(isc_task_t *){ NULL });
2619     			find->event.ev_sender = task;
2620     			find->event.ev_action = action;