MINOR: config: set the bind_conf entry on listeners created from a "listen" line.

MINOR: config: set the bind_conf entry on listeners created from a "listen" line.

Otherwise we would risk a segfault when checking the config's validity
(eg: when looking for conflicts on ID assignments).

Note that the same issue exists with peers_fe and the global stats_fe. All
listeners should be reviewed and simplified to use a compatible declaration
mode.