Add support for keystoneclient 0.4.0

Keystoneclient auth_middleware changed the way it parses the datetime
returned from the cache, breaking the Ceilometer unit tests. This patch
fixes the fake cache system that's used in unit test, so it works with
all keystoneclient versions.

This also update the sample configuration files to include the new
options provided by keystoneclient 0.4.0.

Fixes-Bug: #1238529

Change-Id: Iecfd50d9e9801aeb919f2c09a728e4ea15245a5e