zdtm.py: Call zdtm_mount_cgroups in advance

This script prepares the cgroups hierarchies that are used by
tests to avoid creation of those in parallel with tests, that
do not expect them to appear.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm.py

@@ -349,7 +349,7 @@ class zdtm_test:
 			subprocess.check_call(["make", "zdtm_ct"])
 		if not os.access("zdtm/lib/libzdtmtst.a", os.F_OK):
 			subprocess.check_call(["make", "-C", "zdtm/"])
-
+		subprocess.check_call(["flock", "zdtm_mount_cgroups", "./zdtm_mount_cgroups"])
 
 
 class inhfd_test:

test/zdtm_mount_cgroups

@@ -4,7 +4,7 @@
 # Error (cgroup.c:768): cg: Set 3 is not subset of 2
 # so lets create all test controllers before executing tests.
 
-cat /proc/self/cgroup | grep zdtmtst.defaultroot && exit
+cat /proc/self/cgroup | grep -q zdtmtst.defaultroot && exit
 
 tdir=`mktemp -d zdtm.XXXXXX`
 for i in "zdtmtst" "zdtmtst.defaultroot"; do