MXS-1775 Monitoring function named consistently

The main monitoring function now has the same name in all
monitors (except MariaDBMonitor) and is a member function.

server/modules/monitor/ndbclustermon/ndbclustermon.hh

@@ -37,6 +37,8 @@ private:
     NDBCMonitor(MXS_MONITOR* monitor);
     ~NDBCMonitor();
 
+    void update_server_status(MXS_MONITORED_SERVER *database);
+
     bool has_sufficient_permissions() const;
     void configure(const MXS_CONFIG_PARAMETER* params);
     void tick();