FastBoot still renders the body on redirect

Looks like it's a miss in the implementation as outlined in https://github.com/ember-fastboot/ember-cli-fastboot/pull/195#issue-70081165:

> `transitionTo` still renders the body. The middleware or fastboot could be modified to not include it, but a better solution would be to tell Ember to abort the page rendering. Tips on how to do that would be appreciated. I couldn't find anything straightforward in the docs.

`fastboot` library does not include body for redirects, implemented in commit https://github.com/ember-fastboot/fastboot/commit/3f386fd82cc2d8733d080d3204420223ecc57666.

Since then lot of things have changed in Ember rendering engine and I hope this is feasible/possible to implement to tell Ember not to render anything.

Looks like [`shouldRender` configuration option](https://github.com/ember-fastboot/fastboot#additional-configuration) would result in desired outcome but it's set too early in bootstrap phase.

Any other ideas?