gunit: Add unit tests for cgroup_create_cgroup()

gunit: Add unit tests for cgroup_create_cgroup()

This commit adds unit tests for cgroup_create_cgroup().

[----------] 3 tests from CgroupCreateCgroupTest
[ RUN      ] CgroupCreateCgroupTest.CgroupCreateCgroupV1
[       OK ] CgroupCreateCgroupTest.CgroupCreateCgroupV1 (1 ms)
[ RUN      ] CgroupCreateCgroupTest.CgroupCreateCgroupV2
[       OK ] CgroupCreateCgroupTest.CgroupCreateCgroupV2 (0 ms)
[ RUN      ] CgroupCreateCgroupTest.CgroupCreateCgroupV1AndV2
[       OK ] CgroupCreateCgroupTest.CgroupCreateCgroupV1AndV2 (1 ms)
[----------] 3 tests from CgroupCreateCgroupTest (2 ms total)

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>