Configure rabbitmq credentials in keystone.conf

Rabbitmq credentials in keystone.conf should be updated according
to localrc

This is done mostly to enable keystone notifications.

There are 2 cases where we can use notifications from keystone:
A) Collect audit notifications in ceilometer
B) Collect profiling data

Change-Id: I381d4d670755aa691743caa02df7dc55e05784c2
Merge "Configure rabbitmq credentials in keystone.conf"
Merge commit 'refs/changes/83/86083/2' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch