MINOR: connection: add a pointer to the connection owner

This will be needed to find the stream interface from the connection
once they're detached, but in the more immediate term, we'll need this
for health checks since they don't use a stream interface.
diff --git a/include/proto/stream_interface.h b/include/proto/stream_interface.h
index f68b6ba..c11ce38 100644
--- a/include/proto/stream_interface.h
+++ b/include/proto/stream_interface.h
@@ -67,19 +67,19 @@
 static inline void si_prepare_conn(struct stream_interface *si, const struct protocol *ctrl, const struct data_ops *ops)
 {
 	si->ops = &si_conn_ops;
-	conn_prepare(&si->conn, &si_conn_cb, ctrl, ops);
+	conn_prepare(&si->conn, &si_conn_cb, ctrl, ops, si);
 }
 
 static inline void si_prepare_embedded(struct stream_interface *si)
 {
 	si->ops = &si_embedded_ops;
-	conn_prepare(&si->conn, NULL, NULL, NULL);
+	conn_prepare(&si->conn, NULL, NULL, NULL, si);
 }
 
 static inline void si_prepare_task(struct stream_interface *si)
 {
 	si->ops = &si_task_ops;
-	conn_prepare(&si->conn, NULL, NULL, NULL);
+	conn_prepare(&si->conn, NULL, NULL, NULL, si);
 }
 
 /* Sends a shutr to the connection using the data layer */