Install Guide: Fix service names for Ubuntu and openSUSE

For Ubuntu:
openvswitch->openvswitch-switch
neutron-openvswitch-agent->neutron-plugin-openvswitch-agent
For openSUSE:
neutron-openvswitch-agent->openstack-neutron-openvswitch-agent

Change-Id: I8fa175b9a666a41818c1fc590fc34a9afbb91e32
backport: havana
Closes-Bug: 1246021
(cherry picked from commit 7ec6ae8c616e47559d4a062b3f0a3fc98ac824fa)
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
(cherry picked from commit 56b5bac102ee475cd70e4e92edf5ee69b86be597)
Merge "Install Guide: Fix Open vSwitch plugin/Ubuntu" into stable/havana
Merge "Install Guide: Fix service names for Ubuntu and openSUSE" into stable/havana