Install Guide: Fix Open vSwitch plugin/Ubuntu
Install Guide: Fix Open vSwitch plugin/Ubuntu

It should be neutron-plugin-openvswitch-agent on Ubuntu/Debian

Change-Id: Ib3e081c657657d3395beeda01681a532ac66ee00
backport: havana
Closes-Bug: 1246042
Partial-Bug: 1245914

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