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.
diff --git a/src/mux_h1.c b/src/mux_h1.c
index 0b76ef4..ffec7e8 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -1692,7 +1692,7 @@
 				break;
 
 			default:
-				h1m->flags |= errflag;
+				h1s->flags |= errflag;
 				break;
 		}
 		total += vlen;