BUG/MEDIUM: h2: Call h2_process() if there's an error on the connection.

In h2_recv(), return 1 if there's an error on the connection, not just if
there's a read0 pending, so that h2_process() can be called and act as a
janitor.
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 4914927..336bd4e 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -2258,7 +2258,7 @@
 
 	if (!b_data(buf)) {
 		h2_release_buf(h2c, &h2c->dbuf);
-		return conn_xprt_read0_pending(conn);
+		return (conn->flags & CO_FL_ERROR || conn_xprt_read0_pending(conn));
 	}
 
 	if (b_data(buf) == buf->size)