This commit allows "detaching" to be a valid pending state when
detaching a volume. Despite being obvious pending state, it also
helps in race situations when a volume is implicitly being detached
by Nova.
This commit prevents Terraform from erroring when an attempt is made
to delete a volume already in a "deleting" state. This can happen when
the volume is the root disk of an instance and the instance was
terminated.
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>
This commit follows suit of #1897 by fixing volume-related
parameters which allow the volume attach acceptance test
to work. It also re-enables the volume attach test.
This commit ensures that a volume is detached from all instances
before it is deleted.
It also adds in an `attachment` exported parameter that shows details
of the volume's attachment(s).
