When we try to prefix match the `nomad volume detach` node ID argument, the
node may have been already GC'd. The volume unpublish workflow gracefully
handles this case so that we can free the claim. So make a best effort to find
a node ID among the volume's claimed allocations, or otherwise just use the
node ID we've been given by the user as-is.
Fixes a bug where the `nomad volume detach` command would not accept a node ID
prefix instead of a full node ID. The volume ID is already prefix matched
server-side.
The soundness guarantees of the CSI specification leave a little to be desired
in our ability to provide a 100% reliable automated solution for managing
volumes. This changeset provides a new command to bridge this gap by providing
the operator the ability to intervene.
The command doesn't take an allocation ID so that the operator doesn't have to
keep track of alloc IDs that may have been GC'd. Handle this case in the
unpublish RPC by sending the client RPC for all the terminal/nil allocs on the
selected node.
