libvirt: ROLLING BACK the COMPLETE UNTESTED BLIND BUMP

Seriously, why even bother with the pull request method of submitting
changes when nobody's going to bother testing any of the commits
submitted?  If you're just going to blindly merge stuff without making
sure it works, just don't.

See also: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=757609

Version 1.2.7 of libvirt COMPLETELY FAILS TO WORK if you have qemu
guests.  This isn't a soft failure.  It's a grave, serious, hard
failure.  And yet for some reason, this utterly broken bump was blithely
accepted as being Just Fine, apparently by a bunch of people who don't
even use libvirt so they just said oh hey, new version?  Cool, that must
be Obviously Better.

It's not.

Testing, guys, let's try doing that for once.