Refactor cgroups unit tests
Refactor cgroups unit tests

- Drop areRulesEqual / isRulesInRuleList in favour of builtin Ginkgo's
  comparison and ContainElement;
- Drop redundant mockCgroupManager since it's just passing the all the
  calls to the real manager.

Signed-off-by: Itamar Holder <b6ebf050aad0538d1e30c557853a5c8924b66230@redhat.com>

kubevirt/kubevirt,kubevirt/kubevirt,kubevirt/kubevirt,kubevirt/kubevirt