tools: Show a clearer error message if a server doesn't support WKS
* tools/gpg-wks-client.c (command_send): If we fail to lookup the submission address, print a better error message. If it is because the corresponding file doesn't exist, provide the hint that the server probably doesn't support WKS.
- Signed-off-by: Neal H. Walfield <neal@g10code.com>