Have ssh close stdin and forceallocate pty

Somehow we still need to have a real pty on stdin to ssh so
window-size-thingie works.

scripts/mosh

@@ -244,7 +244,7 @@ if ( $pid == 0 ) { # child
   }
 
   my $quoted_self = shell_quote( $0 );
-  exec "$ssh " . shell_quote( '-S', 'none', '-o', "ProxyCommand=$quoted_self --fake-proxy -- %h %p", '-t', $userhost, '--', "$server " . shell_quote( @server ) );
+  exec "$ssh " . shell_quote( '-S', 'none', '-o', "ProxyCommand=$quoted_self --fake-proxy -- %h %p", '-n', '-tt', $userhost, '--', "$server " . shell_quote( @server ) );
   die "Cannot exec ssh: $!\n";
 } else { # parent
   my ( $ip, $port, $key );