Bugfix: Removing trove and tempest before nova

The barclamps "trove" and "tempest" should be removed before
removing nova. If you don't do that, you can get this error
during installation: "Failed to talk to service delete: 500: Error,
could not delete proposal.Cannot deactivate a proposal for nova,
as it breaks dependencies of tempest-config-default and
trove-config-default."