tracker-extract: Avoid the fluiddec gstreamer plugin

This is a module that attempts to decode MIDI and send it to the
soundcard. We don't want such access triggered from tracker-extract
(and it's actually caught by our seccomp sandbox). Avoid this plugin
altogether.

Fixes: #101

src/tracker-extract/tracker-extract-gstreamer.c

@@ -1404,6 +1404,7 @@ tracker_extract_module_init (GError **error)
 	/* Lifted from totem-video-thumbnailer */
 	const gchar *blocklisted[] = {
 		"bcmdec",
+		"fluiddec",
 		"vaapi",
 		"video4linux2"
 	};