ctdb: add/implement CTDB_CONTROL_TCP_CLIENT_PASSED

ctdb: add/implement CTDB_CONTROL_TCP_CLIENT_PASSED

With multichannel a tcp connection is registered first with
a temporary smbd process, that calls CTDB_CONTROL_TCP_CLIENT
first and then passes the tcp connection to the longterm smbd
that already handles all connections belonging to the specific
client_guid. That smbd process calls CTDB_CONTROL_TCP_CLIENT
again, but the 'tickle' information is already there.
When the temporary smbd process exists/disconnects from ctdb
or calls CTDB_CONTROL_TCP_CLIENT_DISCONNECTED, the 'tickle'
information is removed, while the longterm smbd process
still serves the tcp connection.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15523

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Martin Schwenke <martin@meltin.net>