client.shared.utils_cgoup: Two little modifications in utils_cgroup

Hi guys,

this patchset eases on the system requirements and allows latest distros to run cgroup_tests tests. Please see the details in the actual commits.

Kind regards,
Lukáš

PS: I still have problems executing `cpu_high_load_test` as my system (Fedora 19) always fail when trying to reload the cgroups (`service cgconfig restart`). I need to investigate it a bit.