Remove plugin projects from test-requirements.txt
Remove plugin projects from test-requirements.txt

Plugin projects were listed in test-requirements.txt ostensibly to pull
them in for autodoc building. However, test-requirements.txt wasn't
being used for that purpose -- doc/requirements.txt was, so [1] added
them there. So this commit removes them from test-requirements.txt where
they're unused.

[1] Id9be39971110fd2eb4519a0582c9bf2514cdcacd

Change-Id: Ia89888ee05e17da636ee46894232624e0178d6bc

openstack/python-openstackclient,openstack/python-openstackclient,dtroyer/python-openstackclient,dtroyer/python-openstackclient