cgroup_test: Make user can run part of test cases

1.test.cfg can desire which test case you want to run.
2.Defaultly test.cfg contains all the testcases, you  can modify its detail to run different case.
3.test-example.cfg contains all the testcases, you  can get every testcase name.

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>