Add blurb about using Deckhand client with Keystone Token
Add blurb about using Deckhand client with Keystone Token

This PS simply adds a documentation blurb about how to use the
Decklahdn client via a pre-existing Keystone token.

Other auth plugins can be used with a similar effect. See:

https://github.com/openstack/keystoneauth/tree/edeb84715c80c5299c0f78c872d6507d9093ad82/keystoneauth1/identity/v3

Change-Id: I5bf5a57ec02a7b2bda7304b5c5068f88cea228e1

att-comdev/deckhand,att-comdev/deckhand