Adding heat testcases

1]. Adding Heat Fixture and testcases under heat directory
2]. Modifying the logic in ecmp serial testcases to shut
    the VMs before rebooting the nodes.
3]. Adding a logic to wait till the Stacks are created.
4]. Ran autopep8.
Change-Id: Ibccedd05105500461eadcd6b64f03c83082bbbed
Merge "Adding heat testcases" into R2.0