Add get bottom_id by top_id and region_name test case
Add get bottom_id by top_id and region_name test case

1. What is the problem
Tricircle does not have get bottom id by top_id and
region_name test case

2. What is the solution to the problem
Implement related test case

3. What the features need to be implemented to the Tricircle
No new features

Change-Id: I0ec873f16ff596c28e4c517d6790a3cc1d5f13df

stackforge/tricircle,openstack/tricircle,openstack/tricircle,stackforge/tricircle