webui: fix multiple success messages

fixes #124

one/views.py

@@ -543,7 +543,6 @@ def vm_renew(request, which, iid, *args, **kwargs):
     try:
         vm = get_object_or_404(Instance, id=iid, owner=request.user)
         vm.renew()
-        messages.success(request, _('Virtual machine is successfully renewed.'))
     except:
         messages.error(request, _('Failed to renew virtual machine.'))
         return redirect('/')