Fixes #13356 - OpenStack volumes API v2 needs :name

Our code in uses :display_name as the name attribute to create
Openstack volumes.

Notice volume v2 API requires :name, while v1 just needs :display_name
https://github.com/fog/fog/blob/master/lib/fog/openstack/models/volume_v1/volume.rb
https://github.com/fog/fog/blob/master/lib/fog/openstack/models/volume_v2/volume.rb#L17

So we cannot create Volumes on Openstack when they use the v2 API.
Fix is simple, just add :name in that hash and it works.