Remove references to '24 hour' tokens

The token lifespan used by a deployment is configurable via
`keystone.conf [token] expiration` - it may not be 24 hours.

In fact, bp reduce-default-token-duration recently reduced the default
token duration from 24 hours to just one hour. The keystone community
expects to tweak this value over the next several releases, so I've
avoided using a specific value here to reduce maintenance effort.

https://blueprints.launchpad.net/keystone/+spec/reduce-default-token-duration

Change-Id: I86afd624c2d8ef4de3275ebaf3ceab80ef324f3e
Merge "Remove references to '24 hour' tokens"