Sped up tests by reducing reset button timeout whilst testing

no issue

- tests will wait for everything to settle before continuing or ending so the 2.5sec timeout on task button resets was adding a lot of extra time
- use Ember's environment to see if we're testing and reduce the reset timeout from 2500ms to 50ms

ghost/admin/app/components/gh-task-button.js

@@ -1,4 +1,5 @@
 import Component from '@ember/component';
+import config from 'ghost-admin/config/environment';
 import {computed} from '@ember/object';
 import {isBlank} from '@ember/utils';
 import {reads} from '@ember/object/computed';
@@ -40,6 +41,8 @@ const GhTaskButton = Component.extend({
     failureText: 'Retry',
     failureClass: 'gh-btn-red',
 
+    isTesting: undefined,
+
     // Allowed actions
     action: () => {},
 
@@ -101,6 +104,9 @@ const GhTaskButton = Component.extend({
     init() {
         this._super(...arguments);
         this._initialPerformCount = this.get('task.performCount');
+        if (this.isTesting === undefined) {
+            this.isTesting = config.environment === 'test';
+        }
     },
 
     click() {
@@ -167,7 +173,7 @@ const GhTaskButton = Component.extend({
     }),
 
     _resetButtonState: task(function* () {
-        yield timeout(2500);
+        yield timeout(this.isTesting ? 50 : 2500);
         if (!this.get('task.last.isRunning')) {
             // Reset last task to bring button back to idle state
             yield this.set('task.last', null);