qemu_cgroup: Allow /dev/mapper/control for PR
Just like in previous commit, qemu-pr-helper might want to open
/dev/mapper/control under certain circumstances. Therefore we
have to allow it in cgroups.
The change virdevmapper.c might look spurious but it isn't. After
6dd84f6850ca437 any path that we're allowing in deivces CGroup is
subject to virDevMapperGetTargets() inspection. And libdevmapper
returns ENXIO for the path from subject.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>