Fix EZP-23307: PHP Fatal error: Failed opening required ezpkernelredirec...

...t.php

The wrong currentUser() is returned on post-login redirect, because instance() creates and loads invalid globals cache.

https://jira.ez.no/browse/EZP-23307

Don't ask me to explain the finer details of this, I have no idea. Also, if it passes all tests, I'll book a trip to Las Vegas.