Restore dns_validator_destroy and fetchctx_detach call order

7a78a85b moved the destruction of the validator from near the start
validated to the end.  This reversed the order of dns_validator_destroy
and fetchctx_detach.  Restore the order so that val->name remains
valid for the lifetime of the validator.

lib/dns/resolver.c

@@ -5622,9 +5622,14 @@ cleanup_fetchctx:
 		fctx_done_unref(fctx, result);
 	}
 
+	/*
+	 * val->name points to name on a message on one of the
+	 * queries on the fetch context so the validator has to
+	 * be destroyed first.
+	 */
+	dns_validator_destroy(&val);
 	fetchctx_detach(&fctx);
 	INSIST(node == NULL);
-	dns_validator_destroy(&val);
 }
 
 static void