Get RabbitMQ credentials from hiera
Get RabbitMQ credentials from hiera

Switch tests to use hiera for getting RabbitMQ
credentials, because configuration files for Nova
can be manually modified/removed after deployment,
so AMQP tests shouldn't rely on them.

Change-Id: Ib9b2f24913b3d0fe05079fbd45c872ebaf8c098c
Closes-bug: #1479557

stackforge/fuel-ostf,eayunstack/fuel-ostf,eayunstack/fuel-ostf,stackforge/fuel-ostf