Add link to neutron sanity checker
Add link to neutron sanity checker

As per bug, add link to neutron-sanity-check command-line client.

Change-Id: Idce679be0d1dbefc40cd823b177d0af7399f8f98
Closes-Bug: #1677728

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals