MEDIUM: listener: store the default target per listener

This will be useful later to state that some listeners have to use
certain decoders (typically an HTTP/2 decoder) regardless of the
regular processing applied to other listeners. For now it simply
defaults to the frontend's default target, and it is used by the
session.
diff --git a/src/session.c b/src/session.c
index 7a00b0d..677d3a1 100644
--- a/src/session.c
+++ b/src/session.c
@@ -481,7 +481,7 @@
 		s->si[1].flags |= SI_FL_INDEP_STR;
 
 	session_init_srv_conn(s);
-	s->target = p->default_target; /* used by peers and CLI */
+	s->target = l->default_target; /* used by peers and CLI */
 	s->pend_pos = NULL;
 
 	/* init store persistence */