This commit cleans up the volume and block device handling in the instance
resource. It also adds more acceptance tests to deal with different workflows
of attaching and detaching a volume through the instance's lifecycle.
No new functionality has been added.
When using an image as the source of new volume the state 'downloading'
prior to the state 'available' is fine.
It is also fine to destroy a volume in the state 'downloading'.
Closes-bug: #2865
Co-Authored-By: Joe Topjian <joe@topjian.net>
Joe Topjian