Tweak volume commands

Basic cleanups:
* metadata is one word
* multiple metadata items can be set using multiple --metadata args
* consistent formatting
* do lookups for volume args

Change-Id: Ib6c43f01ad46b395aee8c61e886f42e2a5f5573e
Do lookups for user, project

This requires https://review.openstack.org/26323 in keystoneclient

Change-Id: I55bededbc20b5dcf2833c59eb2b6b069703d8a9a
Merge branch 'volume-keystone' into dt-test