The in-process cache for keystone tokens has been deprecated due to
"incosistent results and high memory usage" with the expectation we
switch to memcached_servers if we want to stay performant.

Add memcache_servers [cache] section to the appropriate servers as the
[DEFAULT]\memcache_servers options was deprecated.

TrivialFix
Related-Id: Ied2b88c8cefe5655a88d0c2f334de04e588fa75a

Change-Id: Ic971bdddc0be3338b15924f7cc0f97d4a3ad2440