ctdb-daemon: Wait for eventd to be ready before connecting

ctdb-daemon: Wait for eventd to be ready before connecting

The current method of retrying the connection to eventd means that
messages get logged for each failure.

Instead, pass a pipe file descriptor to eventd and wait for it to
write 0 to the pipe to indicate that it is ready to accept client
connections.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13592

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
(cherry picked from commit 62ec1ab1470206d6a2cf300f30ca0b4a39413a38)
Signed-off-by: Martin Schwenke <martin@meltin.net>