Tenants API Client - Service Tests Parity

  Refactored tenants-api client to add a list_services method as per service tests parity.
  Refactored tenant_client_test to inherit from object and fixed assertion issues.
  Tested create, delete and list services methods in tenant_client_test.

Change-Id: I032aacac71b563e84063359387a08935c7bb5855
Merge "Tenants API Client - Service Tests Parity"