Updates docs to add OVS support for IPv6 addresses as tunnel endpoints
Updates docs to add OVS support for IPv6 addresses as tunnel endpoints

Fix in the 'OpenStack control & management network considerations'
section. Previously it stated that Open vSwitch does not support
IPv6. This commit updates the documentation now that Open vSwitch
does support IPv6 endpoints.

Change-Id: I3673d033aa4182d012c77f5c13afae692bfc07da
Closes-Bug: #1602403

AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals