Integration tests for Fedora 21

This makes ```TEST_OS=fedora-21 ./VERIFY``` succeed as well.

Open issues:

* Extended DOS Partitions are broken in Fedora 21 [mvollmer]
* cockpit-selinux-policy can not be installed on Fedora 21 [stefw] 
* Existing SELinux policy for cockpit doesn't allow cockpit-ws to read /var/lib/cockpit/ [stefw]
* freeipa-client is missing a dependency [fixed, waiting for package]

Should we have an open bug to reenable this?