The RPC for listing volume snapshots requires a plugin ID. Update the
`volume snapshot list` command to find the specific plugin from the
provided prefix.
The AWS EBS CSI plugin was observed to return a EOF when we get to the end of
the paging for `ListSnapshots`, counter to specification. Handle this case
gracefully, including for `ListVolumes` (which EBS doesn't support but has
similar semantics).
Also fixes a timestamp formatting bug on `ListSnapshots`
