ftests: Add a test to validate cgexec's systemd options (cgroup v2)

ftests: Add a test to validate cgexec's systemd options (cgroup v2)

Add a test case to validate cgexec tool's systemd options on cgroup
unified setup mode.

-----------------------------------------------------------------
Test Results:
        Run Date:                          Feb 05 07:57:18
        Passed:                                  1 test(s)
        Skipped:                                 0 test(s)
        Failed:                                  0 test(s)
-----------------------------------------------------------------
Timing Results:
        Test                              Time (sec)
        --------------------------------------------
        setup                                   0.00
        068-sudo-systemd_cgexec-v2.py           5.53
        teardown                                0.00
        --------------------------------------------
        Total Run Time                          5.53

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