remove explicit version specification from cinder formula

We don't need to specify version explicitly, it is extracted from
service url, before queens it had not led to any problems but since
[1] has been merged  we need to delete explicit specification.

1. https://github.com/openstack/os-client-config/commit/b2f7ceadb1a99bd0f5fb17b9298c6f962414aa9f

Change-Id: I3e153c7fccfb7972a6385757fda459fe46f2bc15
1 file changed