Add timeouts to 'tinc join'

Add timeouts to 'tinc join'

Since server tarpits suspicious connections, `tinc join` doesn't have
the best UX (if anything is broken on server's side, `tinc join` just
hangs indefinitely).

Since we don't want to leak information to the client, add timeouts on
the client side and notify the user that something is amiss if timeout
is reached.