Add volume services schema for microversion 3.7

In volume microversion 3.7, optional attribute cluster is added in the
response body of list_services, so this is to add volume services
schema for volume microversion 3.7.

Change-Id: I4be010dae9b83549b970b117b389626caa2806a0
partially-implements: blueprint fix-microversion-gap
5 files changed