ftests: Add a test to stress create systemd scope via cgcreate

ftests: Add a test to stress create systemd scope via cgcreate

Add a test to stress creation of systemd scope via the cgcreate command
line tool, by passing invalid slice and scope names.

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Test Results:
        Run Date:                          Aug 23 11:03:00
        Passed:                                  1 test(s)
        Skipped:                                 0 test(s)
        Failed:                                  0 test(s)
-----------------------------------------------------------------
Timing Results:
        Test                                   Time (sec)
        -------------------------------------------------
        setup                                        0.00
        997-sudo-cgcreate_systemd_scope.py           0.13
        teardown                                     0.00
        -------------------------------------------------
        Total Run Time                               0.13

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