Add response schema validation for volume hosts

This is to add response schema validation for volume
hosts, also to remove the fields check in testcases.
Besides, there are some inconsistencies in volume hosts api ref,
I36486724cc30389d371ec0b18b9b7f96883d193c will fix them.

Change-Id: I512bfc97a1c3d4a508daf580d99fefe2a9ae4e13
partially-implements: blueprint volume-response-schema-validation
4 files changed