Improve node metadata and upstream connecting mechanism

To handle cascaded replication we're going to have to keep track
of each node's upstream node. Also enumerate the node type
("primary", "standby" or "witness") and mark if active.

repmgrd.c

@@ -432,7 +432,7 @@ main(int argc, char **argv)
 					else if (my_local_mode == STANDBY_MODE)
 					{
 						standby_monitor();
-						log_debug(_("returned from standby_monitor()\n"));
+						log_debug(_("returned from standby_monitor()\n")); // ZZZ
 					}
 					sleep(local_options.monitor_interval_secs);
 
@@ -635,12 +635,13 @@ standby_monitor(void)
 
 	upstream_conn = get_upstream_connection(my_local_conn,
 											local_options.cluster_name,
+											local_options.node,
 											&upstream_node_id, NULL);
 
 
 	/*
-	 * Check if the master is still available, if after 5 minutes of retries
-	 * we cannot reconnect, try to get a new master.
+	 * Check if the upstream node is still available, if after 5 minutes of retries
+	 * we cannot reconnect, try to get a new upstream node.
 	 */
 	check_connection(upstream_conn, "master");	/* this take up to
 												 * local_options.reconnect_atte
@@ -831,7 +832,7 @@ standby_monitor(void)
 					PQerrorMessage(primary_conn));
 }
 
-
+// ZZZ witness
 static void
 do_failover(void)
 {
@@ -865,7 +866,7 @@ do_failover(void)
 
 	/* get a list of standby nodes, including myself */
 	sprintf(sqlquery,
-			"SELECT id, conninfo, witness "
+			"SELECT id, conninfo, type "
 			"  FROM %s.repl_nodes "
 			" WHERE cluster = '%s' "
 			" ORDER BY priority, id "
@@ -896,6 +897,7 @@ do_failover(void)
 	{
 		nodes[i].node_id = atoi(PQgetvalue(res, i, 0));
 		strncpy(nodes[i].conninfo_str, PQgetvalue(res, i, 1), MAXLEN);
+		// ZZZ witness
 		nodes[i].is_witness = (strcmp(PQgetvalue(res, i, 2), "t") == 0) ? true : false;
 
 		/*