CID 462773: Control flow issue in lib/dns/rbt-zonedb.c

Coverity Scan reported the following issue on main.

/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     		/*

Likely stemming from !7873 (merged).