Add 'Nginx' to Glossary
Add 'Nginx' to Glossary

When I fix this bug, I find glossary doesn't mention "Nginx". We
need to add it so that I can make this term consistent.

Change-Id: I82eb6652f594a0a29c42f6c52fe069e1fc4c864d
Partial-Bug: #1619491

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