Add "Yii::$app->end();" after redirect

[bicf]

To avoid the "$application->run();" after the redirect.

Without the end() call, the page will be rendered but not show because of the "302" of the answer, than it will be rendered again.

This's a big wasting resources and, that was my the problem, "burn" the flash messages.

[mikehaertl]

Oops, I totally missed this pull request, sorry. Thanks for pointing that out. I wasn't aware that in yii2 the app is not ended anymore if you call redirect(). That's different from Yii 1.