LMS app doesn't redirect after LTI launch POST

[You should redirect after receiving a `POST`](https://en.wikipedia.org/wiki/Post/Redirect/Get) and this is [just as true when the `POST` is an LTI launch](https://www.imsglobal.org/wiki/step-5-redirect-user) but the app doesn't do this. All of the LTI launch views should be fixed to redirect after post.