zdtm/Makefile: show output for each test

In this case we have another chance to not skip errors.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
zdtm: always show errors

Users don't like errors even if criu returns zero.
So I suggest to start looking at them.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>