MXS-2271 Monitor modifications always go through Monitor::configure()

Previously, runtime monitor modifications could directly alter monitor fields,
which could leave the text-form parameters and reality out-of-sync. Also,
the configure-function was not called for the entire monitor-object, only the
module-implementation.

Now, all modifications go through the overridden configure-function, which calls the
base-class function. As most configuration changes are given in text-form, this
removes the need for specific setters. The only exceptions are the server add/remove
operations, which must modify the text-form serverlist.

server/modules/monitor/clustrixmon/clustrixmonitor.cc

@@ -55,6 +55,11 @@ ClustrixMonitor* ClustrixMonitor::create(const string& name, const string& modul
 
 bool ClustrixMonitor::configure(const MXS_CONFIG_PARAMETER* pParams)
 {
+    if (!MonitorWorker::configure(pParams))
+    {
+        return false;
+    }
+
     m_health_urls.clear();
     m_nodes.clear();