Prevent keymaster bindings from causing failed tests (#976)

no issue
- keymaster bindings could be kept around between tests with references to objects that should have been deleted. This was manifesting itself with a Tags acceptance test failing because one of the key binding tests triggered two actions, one on the route under test and another on a route that was kept around from a previous Error Handling acceptance test (previous test intentionally had an aborted transition so the action in the current test was complaining about the first transition not being complete)
- add guard to ensure that shortcuts can't be registered multiple times on an object
- remove all `default` scope keymaster bindings when destroying a test app instance

ghost/admin/app/mixins/shortcuts.js

@@ -44,7 +44,11 @@ key.setScope('default');
  * Find out more at the keymaster docs
  */
 export default Mixin.create({
+
+    _hasRegisteredShortcuts: false,
+
     registerShortcuts() {
+        if (!this._hasRegisteredShortcuts) {
             let shortcuts = this.get('shortcuts');
 
             Object.keys(shortcuts).forEach((shortcut) => {
@@ -65,6 +69,9 @@ export default Mixin.create({
                     });
                 });
             });
+
+            this._hasRegisteredShortcuts = true;
+        }
     },
 
     removeShortcuts() {
@@ -74,5 +81,10 @@ export default Mixin.create({
             let scope = shortcuts[shortcut].scope || 'default';
             key.unbind(shortcut, scope);
         });
+    },
+
+    willDestroy() {
+        this._super(...arguments);
+        this.removeShortcuts();
     }
 });

ghost/admin/tests/helpers/destroy-app.js

@@ -1,3 +1,4 @@
+/* global key */
 import {run} from '@ember/runloop';
 
 export default function destroyApp(application) {
@@ -6,5 +7,9 @@ export default function destroyApp(application) {
         server.shutdown();
     }
 
+    // extra check to ensure we don't have references hanging around via key
+    // bindings on supposedly destroyed objects
+    key.deleteScope('default');
+
     run(application, 'destroy');
 }