It seems to me most of the clean hooks (used by cgroup*, macvlan* cr_veth*
and mnt_tracefs* were all designed to be run to clean up after the test, no
matter whether it failed or succeeded. Let's always run them, so Andrei
doesn't hate me :D

travis-ci: success for zdtm.py: run --clean hook on test failure
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
CC: Andrei Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>