Additional configuration steps for HEAT on RHEL

Added steps on configuring HEAT service to use
Qpid as the messaging broker.

Updated the editing steps to add keystone_authoken
and ec2authtoken to use openstack-config to modify
the heat.conf file as the other configuration
editing in this section uses openstack-config.

Closes-Bug: 1331050

Change-Id: I1caac81c8b4e019e56c9f1cbf8ad75d938aa3ebb
Merge "Additional configuration steps for HEAT on RHEL" into stable/icehouse