wks: Use unencrypted draft-1 mode for posteo.de

* tools/gpg-wks-client.c (command_send): Allow sending in draft-1
mode.

Obviously Posteo did not implement the current draft and thus it was
not possible to send a request to them. This hack uses the old method
for posteo.de. Not sending it encrypted is okay here because they use
authenticated sending anyway.

• Signed-off-by: Werner Koch <wk@gnupg.org>