BUG/MINOR: listener: Handle allocation error when allocating a new bind_conf

BUG/MINOR: listener: Handle allocation error when allocating a new bind_conf

Allocation error are now handled in bind_conf_alloc() functions. Thus
callers, when not already done, are also updated to catch NULL return value.

This patch may be backported (at least partially) to all stable
versions. However, it only fix errors durung configuration parsing. Thus it
is not mandatory.