Fuel authorization -- 6.0 updates

Document updates to Fuel Authorization being implemented
in 6.0 and 5.1.1

operations: update 6500-fuel-auth with info about new features

user-guide:
- User must supply password for upgrade
- Add --password option for fuel CLI

terminology/Keystone -- an instance of Keystone runs in a container now
  in addition to the instances that run on the target nodes

Change-Id: I44277c97de0ca4c3d9e35cca323e7dbc10b444e0
Partial-Bug: 1384343
Partial-Bug: 1387667
Partial-Bug: 1392289
Partial-Bug: 1392626
Merge "Fuel authorization -- 6.0 updates"