Fix docstring and remove unused variable

Fix error docstring and remove unused variable 'volume ' in
VolumeTransferTestCase.

Change-Id: I6c98af30df88b8f19c23ef5e38e4b5b2eef7436c
Closes-Bug: #1272182
Merge "Fix docstring and remove unused variable"
(Test commit) Change README to reflect Jio's fork of Cinder

Change-Id: I3f26c0a736e63725aec24ca2fa12c707b8e6460f