MXS-1744 Use gtid querying instead of MASTER_GTID_WAIT when waiting for catchup

MASTER_GTID_WAIT uses gtid_slave_pos when comparing to the target gtid. This creates
problems with multi-domain gtids. It's simpler to just query the server for its
gtids repeatedly. Also, the method is now in MariaDBServer.

server/modules/monitor/mariadbmon/utilities.hh

@@ -16,6 +16,7 @@
 #include <maxscale/cppdefs.hh>
 #include <string>
 #include <vector>
+#include <maxscale/json_api.h>
 #include <maxscale/monitor.h>
 
 /** Utility macro for printing both MXS_ERROR and json error */