vdsm: Fix regression introduced by refactoring libvirtvm

Rebasing the changeset of refactoring libvirtvm.py and vm.py into vm.py [1]
caused an accidental removal of changes made in commit 30a4b50 [2].

This commit fixes the mess up of this rebase mess up.

[1]: http://gerrit.ovirt.org/gitweb?p=vdsm.git;a=commit;h=ee082b8
[2]: http://gerrit.ovirt.org/gitweb?p=vdsm.git;a=commit;h=30a4b50

Change-Id: I0eeb53828e1a33e6f0e010f9e17fb2911fda3f45
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=985735
Signed-off-by: Vinzenz Feenstra <vfeenstr@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/17687
Reviewed-by: Dan Kenigsberg <danken@redhat.com>