Neutron requirement overrides entry points

Group based policy's dependency on neutron causes problems when Neutron is installed by devstack (or manually) before GBP.
More specifically, the GBP installation causes Neutron's entry points to be overridden.

The proposal is to move the requirement to test requirements.

Change-Id: Ia45f093859c1fb4004af2c7d601d784576cdd2d5
Closes-Bug: #1376918