Add testcases for volume

Adds tests for those GET API functions that accept params

List_volumes and list_volumes_with_detail for nova volume extension
List_volumes and list_volumes_with_detail for Cinder API
List_snapshots and list_snapshots_with_detail for Cinder API
Fixed typo in volume snapshot json client to make it consistent
with the corresponding xml client method "list_snapshots_with_detail"

Partial-Bug: #1086590

Change-Id: Ie703fa8729d838203c12293a7ce1ce942ec83a81
Merge "Add testcases for volume"