s3-messaging: Fix messaging classes.

s3-messaging: Fix messaging classes.

This has been broken since ff0ac5b0 (May 2007).
Basically all messages were belonging to the General class except for CTDB
messages.
This fixed the message_send_all() function to correctly compute the class, and
fixes registrations to include all they need to cope with the fact not all
messages are of calss general (registrations rotted a bit because as long as
FLAG_MSG_GENERAL was defined the process woould receive all messages).

Signed-off-by: Andreas Schneider <asn@samba.org>