Fix: pacemaker-attrd: remember names of peers from attribute update in case unknown

... in the membership cache, so that we also learn names of non-writers
as early as possible through processing `sync-response` from the writer.

Regression introduced by 85d7a70 (not yet released).

Author: gao-yan

daemons/attrd/attrd_corosync.c

@@ -325,8 +325,13 @@ update_attr_on_host(attribute_t *a, const pcmk__node_status_t *peer,
     // Remember node's XML ID if we're just learning it
     if ((node_xml_id != NULL)
         && !pcmk__str_eq(node_xml_id, prev_xml_id, pcmk__str_none)) {
+        // Remember node's name in case unknown in the membership cache
+        pcmk__node_status_t *known_peer =
+            pcmk__get_node(0, host, node_xml_id,
+                           pcmk__node_search_cluster_member);
+
         crm_trace("Learned %s[%s] node XML ID is %s (was %s)",
-                  a->id, v->nodename, node_xml_id,
+                  a->id, known_peer->name, node_xml_id,
                   pcmk__s(prev_xml_id, "unknown"));
         attrd_set_node_xml_id(v->nodename, node_xml_id);
         if (attrd_election_won()) {