Discrepancy between README.rst and cinder help

1) --version in README should be --os-volume-api-version

2) CINDER_URL should be OS_AUTH_URL

Change-Id: I409634f3025463f2ae9419ddd0d99fa50554a04d
Closes-Bug: 1251385
Merge "Discrepancy between README.rst and cinder help"