Fix v2 volume create api-reference request parameters
Fix v2 volume create api-reference request parameters

This fixes several things:

1. The consistencygroup_id and metadata parameters are optional.
2. Several parameters used were for non-volume types, this changes
   the api-ref to use the proper parameters that have the correct
   descriptions for creating a volume.

At some point the parameter names in parameters.yaml need to have
more descriptive names than the lazy *_1, *_2, etc names so it's
easier to know what a parameter is for,
e.g. volume_description_body_required, but that's for a later
cleanup.

Change-Id: I1fb8ca507c85bfbf0add41b507c014ae995e17d0
Closes-Bug: #1642983

phenoxim/cinder,j-griffith/cinder,eharney/cinder,Datera/cinder,j-griffith/cinder,mahak/cinder,eharney/cinder,mahak/cinder,openstack/cinder,phenoxim/cinder,Datera/cinder,openstack/cinder,ge0rgi/cinder