Test tempest decorators used on integration tests

The follow decorators are tested:
 * test.attr
 * test.stresstest
 * test.services
 * test.skip_because
 * test.requires_ext

Partially implements bp unit-tests

Change-Id: Idb9d99b085b396365e662aa2c7fcfa3751e7bf5a
Merge "Test tempest decorators used on integration tests"
Merge branch 'master' of https://github.com/openstack/tempest