Added clarity for installing Neutron plugin on dedicated controller
Added clarity for installing Neutron plugin on dedicated controller

As reported to Launchpad, the instructions for setting up the Neutron
server on a dedicated controller that will NOT be providing any
underlying functionality are not clear as to why we need to install
and configure the plugin here.

Note, this is a forward port to avoid problems caused with change
Ia4ce1ea618116fa51e847e1bbb9b804ab4c32870

Change-Id: I609d187321c2e0ff82f45fe24118f5b31bef7791
(cherry picked from commit 91711b4350f240d0a12a7f68b6b09c40045e73a6)

AlekhyaMallina-Vedams/openstack-manuals,gongysh2004/openstack-manual,Akasurde/openstack-manuals,kairoaraujo/openstack-manuals,kairoaraujo/openstack-manuals,saeki-masaki/openstack-manuals,openstack/openstack-manuals,Akasurde/openstack-manuals,openstack/openstack-manuals,potsmaster/openstack-manuals,potsmaster/openstack-manuals,gongysh2004/openstack-manual,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,saeki-masaki/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals