zdtm: cleanup zdtmtst and zdtmtst.defaultroot cgroups after finishing test

After running criu test, docker on the node becomes unusable, as it is
confused by our leftover cgroups. Surely docker should be fixed to
ignore custom cgroups (https://github.com/moby/moby/issues/37601), but
we should not leave them after test also.

v2: rmdir the holder only if it exists, remove racy wait and remove
wrongly added cleanup method in class criu
v3: bring back missed semicolon

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

test/zdtm.py

@@ -569,6 +569,10 @@ class zdtm_test:
 			subprocess.check_call(["make", "-C", "zdtm/"])
 		subprocess.check_call(["flock", "zdtm_mount_cgroups.lock", "./zdtm_mount_cgroups"])
 
+	@staticmethod
+	def cleanup():
+		subprocess.check_call(["flock", "zdtm_mount_cgroups.lock", "./zdtm_umount_cgroups"])
+
 
 class inhfd_test:
 	def __init__(self, name, desc, flavor, freezer):
@@ -674,6 +678,10 @@ class inhfd_test:
 	def available():
 		pass
 
+	@staticmethod
+	def cleanup():
+		pass
+
 
 class groups_test(zdtm_test):
 	def __init__(self, name, desc, flavor, freezer):
@@ -2200,3 +2208,6 @@ for tst in test_classes.values():
 	tst.available()
 
 opts['action'](opts)
+
+for tst in test_classes.values():
+	tst.cleanup()

test/zdtm_umount_cgroups

@@ -0,0 +1,16 @@
+#!/bin/sh
+
+# Lets delete all test controllers after executing tests.
+
+cat /proc/self/cgroup | grep -q zdtmtst.defaultroot || exit 0
+
+tdir=`mktemp -d zdtm.XXXXXX`
+for i in "zdtmtst" "zdtmtst.defaultroot"; do
+	mount -t cgroup -o none,name=$i zdtm $tdir || { rmdir $tdir; exit 1; }
+	# remove a fake group if exists
+	if [ -d "$tdir/holder" ]; then
+		rmdir $tdir/holder || { umount -l $tdir && rmdir $tdir; exit 1; }
+	fi
+	umount -l $tdir || exit 1;
+done
+rmdir $tdir