Fix the removal of skip_unless_config decorator in Tempest

That decorator was not really useful as there's already a similar
decorator in testtools.

Note, I am still going to propose something (worst case a revert) to
fix the already released version of this Tempest plugin.

Change-Id: I578c5b5e1c83aa7a41a334a49eceff2b90a60767
2 files changed