Support userspace disk URIs for OS import/export scripts

Also handle the case where a disk is accessible by URI only. Support
for the other OS scripts was added in commits
e147e00863fcf24f40fd8d9c9349d1fbce079c81 and
c4f1bff731492b73515089fdfd1c3482be05439c, but import/export scripts
have some additional cases to handle.

Signed-off-by: Nicolas Avrutin <rasputin@google.com>
Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>
2 files changed