Fixes two doc bugs with networking install and admin

(- ensures network-admin/admin is redirected as people are finding it)
- ensures ubuntu output has ovs install instruction

Not backported: ../www/.htaccess

Change-Id: I22cafaae77e247d8cc2a3d01cd1bfb8320b6efb3
backport: havana
Closes-bug: 1248791
(cherry picked from commit a8ce414fa76a17286cb5fd4bd489378120cfed3e)