Do not initialize all the application if another instance is running

This fixes a crash becasue we were constructing the systemtray and then
destroying it too early before the systemtray could initilize itself.
(This work around a bug in QSystemTray which crashes if it is destroyed
before it is registered to the X11 server)

src/main.cpp

@@ -35,7 +35,6 @@ int main(int argc, char **argv)
     Q_INIT_RESOURCE(mirall);
 
     Mirall::Application app(argc, argv);
-    app.initialize();
 #ifndef Q_OS_WIN
     signal(SIGPIPE, SIG_IGN);
 #endif

src/mirall/application.cpp

@@ -95,6 +95,10 @@ Application::Application(int &argc, char **argv) :
     //no need to waste time;
     if ( _helpOnly ) return;
 
+    initialize();
+    if (isRunning())
+        return;
+
     setupLogging();
     setupTranslations();