ftests/060: Add new systemd error message

ftests/060: Add new systemd error message

systemd >= 252 has changed the error message on creating duplicate
transient units, upstream commit 1f83244641f1 ("manager: allow transient
units to have drop-ins"). Adopt the newer systemd error message to avoid
expected failure.

-----------------------------------------------------------------
Test Results:
        Run Date:                          May 26 07:03:01
        Passed:                                  1 test(s)
        Skipped:                                 0 test(s)
        Failed:                                  0 test(s)
-----------------------------------------------------------------
Timing Results:
        Test                                   Time (sec)
        -------------------------------------------------
        setup                                        0.00
        060-sudo-cgconfigparser-systemd.py           3.62
        teardown                                     0.00
        -------------------------------------------------
        Total Run Time                               3.62

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