Given that the previous issues caused spurious worker socket wakeups in
the master for inherited FDs that couldn't be closed, let's add a strict
test in the I/O callback to make sure that an accept() event is always
caught by the appropriate type of process (master for master listeners,
worker for worker listeners).
if (!l)
return;
+ BUG_ON(!!master != !!(l->rx.flags & RX_F_MWORKER));
listener_accept(l);
}