BUG/MINOR: http: disable compression when message has no body

Compression was not disabled on 1xx, 204, 304 nor HEAD requests. This
is not really a problem, but it reports more compressed responses than
really done.
diff --git a/src/proto_http.c b/src/proto_http.c
index 6f1b9d7..3184e24 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -5136,6 +5136,7 @@
 	    (txn->status >= 100 && txn->status < 200) ||
 	    txn->status == 204 || txn->status == 304) {
 		msg->flags |= HTTP_MSGF_XFER_LEN;
+		s->comp_algo = NULL;
 		goto skip_content_length;
 	}