Remove requirements.txt from tox.ini
Remove requirements.txt from tox.ini

pbr now reflects the package dependencies from requirements.txt into
sdist that tox builds. No necessary to add it in the test env.

Change-Id: I8f65dd20da90dfde584d28448cfd0039e11e25ec

stackforge/senlin,openstack/senlin,stackforge/senlin,tengqm/senlin-container,Alzon/senlin,openstack/senlin,openstack/senlin,Alzon/senlin,tengqm/senlin-container