Patched UDisks2 -> storaged, for real now

Hi, Cockpit master now uses storaged instead of the patched UDisks2, and cockpit-deps has been cleanup accordingly. Yay! There is also a new "cockpit" flavored image for the test suite. The 'testsuite-prepare' script should pick it up automatically. It's probably necessary to run "./make-rpms --clean" once to flush the old UDisks2 out of your build chroots, but it shouldn't do any harm there. This means that all (three! :-) pending pull requests are now broken until they are rebased to master. That's not a problem, of course, and I'll do that soonish (if nobody beats me to it).