selftests: cgroup: Make cg_create() use 0755 for permission instead of 0644

commit b09c2baa upstream.

0644 is an odd perm to create a cgroup which is a directory. Use the regular
0755 instead. This is necessary for euid switching test case.

Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>