BUG/MEDIUM: h2: Don't try to chunk data when using HTX.

When we're using HTX, we don't have to generate chunk header/trailers, and
that ultimately leads to a crash when we try to access a buffer that
contains just chunk trailers.

This should not be backported.
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 2c8d1cc..b0b891a 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -3101,7 +3101,7 @@
 		/* a payload is present */
 		if (msgf & H2_MSGF_BODY_CL)
 			h2s->flags |= H2_SF_DATA_CLEN;
-		else if (!(msgf & H2_MSGF_BODY_TUNNEL))
+		else if (!(msgf & H2_MSGF_BODY_TUNNEL) && !htx)
 			h2s->flags |= H2_SF_DATA_CHNK;
 	}