Fix Get Volume Driver Capabilities Spec
Fix Get Volume Driver Capabilities Spec

In the current spec, well defined capabilities have 'cinder_'
prefix.
However, instead of adding 'cinder_' to well defined capabilities,
using vendor name + colon(:) as a prefix for vendor unique
capabilities and using without prefix for well defined capabilities
are more reasonable, because admin can understand which vendor
provides these capabilities in one glance.

This patch fixes these definition in the current spec.

Change-Id: Ic1689352499a0011c152ea9177701c92ad7195b9

openstack/cinder-specs