convert heat templates to use CONFIG_AMQP_ variables

The heat_cfn.pp and heat_cloudwatch.pp templates were still referenceing
obsolete CONFIG_QPID_* variables.  This patch updates packstack to
select either rabbitmq or qpid based templates using get_mq(), and adds
heat_qpid.pp as a complement to the existing heat_rabbitmq.pp.

This patch also corrects a variable name (rabbit_user --> rabbit_userid)
and an rpc implementation name (heat.openstack.common.rpc.impl_rabbit ->
heat.openstack.common.rpc.impl_kombu).

Change-Id: I9494d64eb4ed92984c563a215d432f93e3003dfc
Closes-bug: 1295810