Updated neutron.conf to reflect new RPC options

Updated neutron.conf to reflect new RPC options

After oslo.messaging port, some option became unavailable to set, some
of them changed description or default values. Make sure we don't leave
anything related to old RPC layer there.

New entries are generated by calling the following from inside
oslo-incubator:

$ python openstack/common/config/generator.py -l oslo.messaging

blueprint oslo-messaging

Change-Id: I1523309cf0cd92a5d5f0b265f49979b3e47c2afa