Fix quickstart links

Checking http://files.openstack.org/docs-404s/2017-09-08.txt the link
/kolla-ansible/latest/quickstart.html gives a 404 and is most wanted.

The link now is /kolla-ansible/latest/user/quickstart.html - let's
update in tree docs for this.

Fix other broken links as well - with using intra-links instead of
external links - this will make it easier to notice breakage when files
are moved.

Change-Id: I62655afd9f270fa83c07d86aa91346af6337ca32