disable page reloading while migrating vm and pleaseWaitDialog is displayed

fixes: http redirect after migrate does not jump to new compute node

templates/pleasewaitdialog.html

@@ -18,8 +18,10 @@
 <script>
 function showPleaseWaitDialog() {
     $('#pleaseWaitDialog').modal();
+    backgroundJobRunning = true;
 }
 function hidePleaseWaitDialog() {
     $('#pleaseWaitDialog').modal('hide');
+    backgroundJobRunning = false;
 }
 </script>