Bug fix, match tooltip timezone to X-axis timezone (#4855)

* Bug fix, match tooltip timezone to X-axis timezone

* Small improvement

public/app/features/dashboard/dashboardSrv.js

@@ -184,6 +184,7 @@ function (angular, $, _, moment) {
     p.formatDate = function(date, format) {
       date = moment.isMoment(date) ? date : moment(date);
       format = format || 'YYYY-MM-DD HH:mm:ss';
+      this.timezone = this.getTimezone();
 
       return this.timezone === 'browser' ?
         moment(date).format(format) :