Also package mistral_tempest_tests
Also package mistral_tempest_tests

With the current setup.cfg, the folder mistral_tempest_tests is not
being packaged, making it more difficult for package maintainer like
myself to run tempest tests. Please allow this change, so that I don't
have to carry such a patch in the Debian package.

Change-Id: I5c34f3516c4f171ab4f34647f1cc4a08883feacf

StackStorm/mistral,StackStorm/mistral,openstack/mistral,openstack/mistral