Restore the IS_STUB() condition in zone_zonecut_callback
After the refactoring the condition whether to use DNAME or NS for the zonecut was incorrectly simplified and the !IS_STUB() condition was removed. This was flagged by Coverity as:
/lib/dns/rbt-zonedb.c: 192 in zone_zonecut_callback()
186 found = ns_header;
187 search->zonecut_sigheader = NULL;
188 } else if (dname_header != NULL) {
189 found = dname_header;
190 search->zonecut_sigheader = sigdname_header;
191 } else if (ns_header != NULL) {
>>> CID 462773: Control flow issues (DEADCODE)
>>> Execution cannot reach this statement: "found = ns_header;".
192 found = ns_header;
193 search->zonecut_sigheader = NULL;
194 }
195
196 if (found != NULL) {
197 /*
Instead of removing the extra block, restore the !IS_STUB() condition for the first if block.
Closes #4212 (closed)