MEDIUM: stream-int: use si_task() to retrieve the task from the stream int

We go back to the session to get the owner. Here again it's very easy
and is just a matter of relative offsets. Since the owner always exists
and always points to the session's task, we can remove some unneeded
tests.
diff --git a/src/session.c b/src/session.c
index f271e41..7f726d4 100644
--- a/src/session.c
+++ b/src/session.c
@@ -1750,10 +1750,8 @@
 	rpf_last = s->res.flags & ~CF_MASK_ANALYSER;
 
 	/* we don't want the stream interface functions to recursively wake us up */
-	if (s->req.prod->owner == t)
-		s->req.prod->flags |= SI_FL_DONT_WAKE;
-	if (s->req.cons->owner == t)
-		s->req.cons->flags |= SI_FL_DONT_WAKE;
+	s->req.prod->flags |= SI_FL_DONT_WAKE;
+	s->req.cons->flags |= SI_FL_DONT_WAKE;
 
 	/* 1a: Check for low level timeouts if needed. We just set a flag on
 	 * stream interfaces when their timeouts have expired.