encode: write status immediate for success response for CONNECT requests (#6738)

* encode: write status immediate for success response for CONNECT requests

* fix compile

* fix test

* fix lint

* treat first write and flush for encode response writer to CONNECT request as success if status is not set explicitly

modules/caddyhttp/encode/encode_test.go

@@ -9,7 +9,7 @@ import (
 func BenchmarkOpenResponseWriter(b *testing.B) {
 	enc := new(Encode)
 	for n := 0; n < b.N; n++ {
-		enc.openResponseWriter("test", nil)
+		enc.openResponseWriter("test", nil, false)
 	}
 }