Fixing invalid location issue with id extractor

Change-Id: I56df7720eb479d3dfadd9652435353b12fdb03a1
Tenants API Role Model - Role Tests Parity

1. Added and tested methods in tenants-api role model
2. Fixed serialization/deserialization issues for role tests parity.
3. Added and tested _obj_to_json method in tenants-api role model.
4. Fixed reviewer comments - line continuation issues.

Change-Id: Ia84e69fc883da58bd83a49d54b735945735741a9
Merge "Fixing invalid location issue with id extractor"
Merge "Tenants API Role Model - Role Tests Parity"
Added client and model for the UsedLimitsForAdmin extension

Created client and model to describe the UsedLimitsForAdmin extension
Changed the location to extensions under compute

Change-Id: Ia8e275664ebd7c1aaf8d75403850b75d7c1d6140