Notify applets that are added to panels about their new constraints too.

This fixes the system tray not updating when being removed and then readded
to the panel. Tasks still doesn't work though. :(

svn path=/trunk/KDE/kdebase/workspace/libs/plasma/; revision=754326

containment.cpp

@@ -458,6 +458,10 @@ Applet* Containment::addApplet(const QString& name, const QVariantList& args, ui
             d->applets.insert(index, applet);
         }
 
+        //the applet needs to be given constraints before it can set its geometry
+        applet->updateConstraints(Plasma::AllConstraints);
+        applet->flushUpdatedConstraints();
+
         break;
     }