fix(VMenu): hover stuck open when mouse exits page (#5844)

fixes #5843
Fix for #5843 - in the event isActive has been reset to false between the time runDelay(open) was called and when we were provisioned this animation frame, sync up hasJustFocused to false and do a no-op assign to isContentActive which doesn't trigger the watcher. Resolve the promise although it's not really needed, just so we aren't breaking promises.

packages/vuetify/src/mixins/menuable.js

@@ -329,7 +329,7 @@ export default Vue.extend({
     },
     startTransition () {
       return new Promise(resolve => requestAnimationFrame(() => {
-        this.isContentActive = true
+        this.isContentActive = this.hasJustFocused = this.isActive
         resolve()
       }))
     },