BUG/MINOR: mux-h1: errflag must be set on H1S and not H1M during output processing

This bug is in an unexpected clause of the switch..case, inside
h1_process_output(). The wrong structure is used to set the error flag.

This patch must be backported to 1.9.

src/mux_h1.c

@@ -1692,7 +1692,7 @@ static size_t h1_process_output(struct h1c *h1c, struct buffer *buf, size_t coun
 				break;
 
 			default:
-				h1m->flags |= errflag;
+				h1s->flags |= errflag;
 				break;
 		}
 		total += vlen;