Fixes Cinder REST API /volumes issue

Fixes Cinder REST API /volumes issue

Issue #1
Once GET variable 'offset' is specified, the API /volume will get an empty
output.

Issue #2
Should validate the GET variable 'limit' before query database to get a
consistent message with Cinder REST API v1.
By current implement, error message is as below if the variable 'limit'
is invalid:
--------------------------------------------------------------------------
{"computeFault": {"message": "The server has either erred or is incapable
of performing the requested operation.", "code": 500}}

After this change, the new message is as below:
--------------------------------------------------------------------------
{"badRequest": {"message": "limit param must be an integer", "code": 400}}

Fixes Bug: 1154454

Change-Id: Ifb155477bae0ea3e39877737ee9019e7d8a104a7