call update_node_record_set_upstream() for STANDBY FOLLOW

repmgrd correctly updates ID of the upstream node after automatic
failover, but repmgr was not doing that for manual failvers.

This moves the existing function to dbutils and modifies it so that
it does not rely on global variables with configuration (available
just in repmgrd).

This should fix issue #67 (hopefully, haven't done much testing).

dbutils.c

@@ -1283,3 +1283,36 @@ create_event_record(PGconn *conn, t_configuration_options *options, int node_id,
 
 	return success;
 }
+
+bool
+update_node_record_set_upstream(PGconn *conn, char *cluster_name, int this_node_id, int new_upstream_node_id)
+{
+	PGresult   *res;
+	char		sqlquery[QUERY_STR_LEN];
+
+	log_debug(_("update_node_record_set_upstream(): Updating node %i's upstream node to %i\n"), this_node_id, new_upstream_node_id);
+
+	sqlquery_snprintf(sqlquery,
+					  "  UPDATE %s.repl_nodes "
+					  "     SET upstream_node_id = %i "
+					  "   WHERE cluster = '%s' "
+					  "     AND id = %i ",
+					  get_repmgr_schema_quoted(conn),
+					  new_upstream_node_id,
+					  cluster_name,
+					  this_node_id);
+	res = PQexec(conn, sqlquery);
+
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+	{
+		log_err(_("Unable to set new upstream node id: %s\n"),
+				PQerrorMessage(conn));
+		PQclear(res);
+
+		return false;
+	}
+
+	PQclear(res);
+
+	return true;
+}