stats: return domain lockspace status

Change-Id: I7069781f9945b4e4637b769a22562de30a6d681d
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/20099
Reviewed-by: Ayal Baron <abaron@redhat.com>
Reviewed-by: Sergey Gotliv <sgotliv@redhat.com>
Tested-by: Sandro Bonazzola <sbonazzo@redhat.com>