ftests: add code to stress cgroup_init()

ftests: add code to stress cgroup_init()

This test case stress cgroup_init(), by trying to create 102 mount
points and indirectly testing the cgroup initialization code, which
would populate the cg_mount_table[] and controllers[].

-----------------------------------------------------------------
Test Results:
        Run Date:                          May 17 11:05:47
        Passed:                                  1 test(s)
        Skipped:                                 0 test(s)
        Failed:                                  0 test(s)
-----------------------------------------------------------------
Timing Results:
        Test                          Time (sec)
        ----------------------------------------
        setup                               0.00
        999-stress-cgroup_init.py           1.91
        teardown                            0.00
        ----------------------------------------
        Total Run Time                      1.91

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>