MXS-2271 Move connection settings inside settings struct

Since the settings are now protected fields, all related functions were
moved inside the monitor class. mon_ping_or_connect_to_db() is now a method
of MXS_MONITORED_SERVER. The connection settings class is defined inside the
server since that is the class actually using the settings.

server/modules/monitor/clustrixmon/clustrixnode.hh

@@ -160,7 +160,7 @@ public:
         m_pServer->is_active = false;
     }
 
-    bool can_be_used_as_hub(const Monitor& mon);
+    bool can_be_used_as_hub(const MXS_MONITORED_SERVER::ConnectionSettings& sett);
 
     SERVER* server() const
     {