Use Zaqar for software-config metadata and signaling

Zaqar provides a simple messaging service which allows heat and orchestrated
services to efficiently communicate with each other, which make it ideal for
software-config metadata distribution and signaling

Change-Id: Ie6fdf42670a79e8e0b0a8e433819ac92e6a1658f
Merge "Use Zaqar for software-config metadata and signaling"