The python 3.8 unit test jobs are failing on a
mock.Mock(spec=secrets.Secret) call. Since this is legacy code and
we don't really need to be testing python-barbicanclient code here,
I'm removing the spec= for these tests to stop artificial failures
when running unit tests on python 3.8.
Change-Id: I9132e2d05bf67ddff4f2d7879d799c8dd25bd3c7