minor findnode optimization

when searching for a node so that we can delete an rdataset,
it is not necessary to set the 'create' flag. if the node doesn't
exist yet, we wouldn't be able delete anything from it.

lib/dns/resolver.c

@@ -5190,7 +5190,7 @@ validated(void *arg) {
 			result = ISC_R_NOTFOUND;
 			if (val->rdataset != NULL) {
 				result = dns_db_findnode(fctx->cache, val->name,
-							 true, &node);
+							 false, &node);
 			}
 			if (result == ISC_R_SUCCESS) {
 				(void)dns_db_deleterdataset(fctx->cache, node,
@@ -5815,7 +5815,6 @@ cache_name(fetchctx_t *fctx, dns_name_t *name, dns_message_t *message,
 	/*
 	 * Find or create the cache node.
 	 */
-	node = NULL;
 	result = dns_db_findnode(fctx->cache, name, true, &node);
 	if (result != ISC_R_SUCCESS) {
 		return (result);