This reverts commit bce27811dfea634118fdb609289ac70c8d4a6854.
Reason for revert: neutron-fwaas has maintainers so the documentation should be available.
Due to changes since the original deletion commit the following changes
were added:
* Add note that OVN is not yet supported
* Remove note that Horizon support is not available
Change-Id: I1a739ee045b49e9b44283c28f95b1accc8a1e37f
7c4f273ed9