Add sphinxcontrib.httpdomain to test-requirements
Add sphinxcontrib.httpdomain to test-requirements

* rtfd docs builds are failing due to missing lib [1]
* add the missing lib to test-requirements so we can publish latest docs
* removed test_service to make gate stable

[1]: https://readthedocs.org/builds/cue/2946531/

Change-Id: I211bd5f4efd0e5e6e8d258d58d3377553b6d5ed7

openstack/cue,stackforge/cue,openstack/cue,openstack/cue,stackforge/cue,stackforge/cue