db/update/Walk: use GetFilenameSuffix() instead of uri_get_suffix()

Unlike GetFilenameSuffix(), uri_get_suffix() removes the query string
first, which breaks file names with question marks in the name.
Therefore, uri_get_suffix() shall only be applied to remote URIs.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1316

src/decoder/Thread.cxx

@@ -395,10 +395,12 @@ TryContainerDecoder(DecoderBridge &bridge, Path path_fs,
 static bool
 decoder_run_file(DecoderBridge &bridge, const char *uri_utf8, Path path_fs)
 {
-	const auto suffix = uri_get_suffix(uri_utf8);
-	if (suffix.empty())
+	const char *_suffix = PathTraitsUTF8::GetFilenameSuffix(uri_utf8);
+	if (_suffix == nullptr)
 		return false;
 
+	const std::string_view suffix{_suffix};
+
 	InputStreamPtr input_stream;
 
 	try {