wks: Do not use compression for the encrypted data.

* tools/gpg-wks-client.c (encrypt_response): Add arg -z0.
* tools/gpg-wks-server.c (encrypt_stream): Ditto.

If for example a server was built without the development packages of
the compression libraries installed, the server will not be able to
decrypt a request. In theory this can't happen due to the preference
system but it is just to easy to create the server's key using a
different version of gpg and then use gpg-wks-server built
differently.

For the short messages we exchange compression is not really required
and thus we better do without to make the system more robust.

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