clusterer: Fix missing lock_release() on "out of PKG"

Credits to @ryancaicse for the report in #2714

(cherry picked from commit 3b26cc5)

modules/clusterer/node_info.c

@@ -877,6 +877,7 @@ clusterer_node_t *api_get_next_hop(int cluster_id, int node_id)
 	lock_get(dest_node->lock);
 
 	if (add_clusterer_node(&ret, dest_node->next_hop) < 0) {
+		lock_release(dest_node->lock);
 		LM_ERR("Failed to allocate next hop\n");
 		return NULL;
 	}