[MEDIUM] session: account per-listener connections

In order to merge the unix session handling code, we have to maintain
the number of per-listener connections in the session. This was only
performed for unix sockets till now.
diff --git a/src/session.c b/src/session.c
index 5213dcd..1a18790 100644
--- a/src/session.c
+++ b/src/session.c
@@ -1206,6 +1206,13 @@
 	if (s->flags & SN_BE_ASSIGNED)
 		s->be->beconn--;
 	actconn--;
+	s->listener->nbconn--;
+	if (s->listener->state == LI_FULL &&
+	    s->listener->nbconn < s->listener->maxconn) {
+		/* we should reactivate the listener */
+		EV_FD_SET(s->listener->fd, DIR_RD);
+		s->listener->state = LI_READY;
+	}
 
 	if (unlikely((global.mode & MODE_DEBUG) &&
 		     (!(global.mode & MODE_QUIET) || (global.mode & MODE_VERBOSE)))) {