zdtm: add missing entries to test/zdtm/.gitignore

This adds new tests "cgroup00" and "clean_mntns" to the .gitignore file.
Signed-off-by: Filipe Brandenburger <filbranden@google.com>
Acked-by: Andrew Vagin <avagin@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/.gitignore

@@ -3,9 +3,11 @@
 /live/static/bind-mount
 /live/static/busyloop00
 /live/static/caps00
+/live/static/cgroup00
 /live/static/child_opened_proc
 /live/static/chroot
 /live/static/chroot-file
+/live/static/clean_mntns
 /live/static/cmdlinenv00
 /live/static/cow00
 /live/static/cow01