Implement qos support

This patch enables Cinder v1/v2 QoS API support, adding following
subcommands to cinder client:
 * create QoS Specs
  cinder qos-create <name> <key=value> [<key=value> ...]
 * delete QoS Specs
  cinder qos-delete [--force <True|False>] <qos_specs>
  'force' is a flag indicates whether to delete a 'in-use' qos specs,
  which is still associated with other entities (e.g. volume types).
 * update QoS Specs
  - add new key/value pairs or update existing key/value
   cinder qos-key <qos_specs_id> set key=value [key=value ...]
  - delete key/value pairs
   cinder qos-key <qos_specs id> unset key [key ...]
 * associate QoS Specs with specified volume type
   cinder qos-associate <qos_specs_id> <volume_type_id>
 * disassociate QoS Specs from specified volume type
   cinder qos-disassociate <qos_specs_id> <volume_type_id>
 * disassociate QoS Specs from all associated volume types
   cinder qos-disassociate-all <qos_specs>
 * query entities that are associated with specified QoS Specs
   cinder qos-get-associations <qos_specs_id>
 * list all QoS Specs
   cinder qos-list

DocImpact

Change-Id: Ie1ddd29fede8660b475bac14c4fc35496d5fe0bc
Merge "Implement qos support"