nova.conf currently uses the [neutron] "url" parameter which has been
deprecated since 17.0.0. In multi-region environments this can
cause Nova to look up the Neutron endpoint for a different region.
Remove this parameter and set region_name and
valid_interfaces to allow the correct lookup to be performed.
Change-Id: I1bbc73728439a460447bc8edd264f9f2d3c814e0
Closes-Bug: #1836952