Calendar: force-rebuild the calendar when the events change

Don't overoptimize and skip the rebuild when the month is the same,
as the calendar depends on the events too.

https://bugzilla.gnome.org/show_bug.cgi?id=726119

js/ui/calendar.js

@@ -420,8 +420,10 @@ const Calendar = new Lang.Class({
     setEventSource: function(eventSource) {
         this._eventSource = eventSource;
         this._eventSource.connect('changed', Lang.bind(this, function() {
+            this._rebuildCalendar();
             this._update();
         }));
+        this._rebuildCalendar();
         this._update();
     },