I noticed that domain names passed as CLI arguments to sshuttle are resolved locally via socket.getaddrinfo. In some cases the name is only resolvable by the remote host (e.g. private VPCs), which I think is the use case for --dns. In such a situation, the script fails with Unable to resolve address ...

I propose to allow resolving the names on the remote machines if --dns appears in the command; either always, or only if the name cannot be resolved, if backward compatibility is a concern in this case.

Related to #844