Fix Error 500 due to stale cache when projects are renamed or transferred

Steps to reproduce:

1. Import a project forktest1 from https://gitlab.com/gitlab-com/www-gitlab-com.git
2. Rename this project to forktest2
3. Re-imported same project into forktest1
4. Error 500

Main issue is that the exists? key was not expired after a rename.

For project transfers, nothing was being expired, which could lead to problems too.

Closes gitlab-org/gitlab-ee#506 and many other issues raised in the last month in CE and Support Forums