ctdb-daemon: Provide a default location for public addresses file

ctdb-daemon: Provide a default location for public addresses file

If the specified file or the default does not exist then log a
warning.

This is done in the takeover code to localise the handling of the
public addresses file.  Soon the daemon command-line option will go
away and the takeover code will be replaced in the not too distant
future.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>