MINOR: compression: init before deleting headers

Init the compression algorithm before modifying the response headers. So
if the compression init fail, the headers won't be modified.
diff --git a/src/proto_http.c b/src/proto_http.c
index 7f2c806..cd13049 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -2087,6 +2087,10 @@
 
 	ctx.idx = 0;
 
+	/* initialize compression */
+	if (s->comp_algo->init(&s->comp_ctx, 1) < 0)
+		goto fail;
+
 	/* remove Content-Length header */
 	if ((msg->flags & HTTP_MSGF_CNT_LEN) && http_find_header2("Content-Length", 14, res->p, &txn->hdr_idx, &ctx))
 		http_remove_header2(msg, &txn->hdr_idx, &ctx);
@@ -2110,10 +2114,6 @@
 		http_header_add_tail2(&txn->rsp, &txn->hdr_idx, trash.str, trash.len);
 	}
 
-	/* initialize compression */
-	if (s->comp_algo->init(&s->comp_ctx, 1) < 0)
-		goto fail;
-
 	return 1;
 
 fail: