Wait reload is done before enable the button

We must return the promise of the reload as the button promise to avoid enable
back the button before the screen is fully reloaded.

issue8488
review249661002

src/screen.js

@@ -1777,7 +1777,7 @@
         button: function(attributes) {
             var ids;
             var process_action = function(action) {
-                this.reload(ids, true).then(function() {
+                return this.reload(ids, true).then(function() {
                     if (typeof action == 'string') {
                         this.client_action(action);
                     }