Update Keystone sample config file

pep8 in Jenkins fails becase it's building with Keystone
client 0.7.0, but the sample config file was generated with
0.6.0. The failure is caused by changes in some descriptions
of configuration items.

Closes-Bug: #1297977
Change-Id: Iad39d1b77274ddf40b55f167bc76d5d24b5c9cd8