Add response schema validation for volume pools

This is to add response schema validation for volume pools.
Besides, free_capacity and total_capacity in "List all back-end
storage pools" should be free_capacity_gb and total_capacity_gb,
Ic0690d12147fa63b903f3442eccde88c1d501711 will fix them.

Change-Id: I8ae2cd178b91756bb488c02a1a2fcdf64f572155
partially-implements: blueprint volume-response-schema-validation
3 files changed