CartridgeRepository#install: Don't keep context

Don't preserve the context when installing a cartridge into the cartridge
repository.  The cartridge needs to be relabeled using the default
contexts.

This commit fixes bug 999117.
Merge pull request #4468 from Miciah/bug-999117–oo-admin-cartridge-a-install-does-not-restorecon-the-installed-cartridge

Merged by openshift-bot