test: use .pid.inprogress file for macvlan test

Note, this depends on Pavel's patch here:
https://lists.openvz.org/pipermail/criu/2016-October/032499.html

 which is
not yet applied.

travis-ci: success for test: use .pid.inprogress file for macvlan test (rev2)
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>