CC-5226: Metadata isn't correct during playing

-fixed using "insert_metadata" and callbacks instead.

python_apps/pypo/liquidsoap_scripts/ls_lib.liq

@@ -5,7 +5,8 @@ def notify(m)
 end
 
 def notify_queue(m)
-  queue_metadata := m
+  f = !dynamic_metadata_callback
+  ignore(f(m))
   notify(m)
 end
 
@@ -31,10 +32,6 @@ def append_title(m) =
   end
 end
 
-def queue_metadata_callback(m) =
-    !queue_metadata
-end
-
 def crossfade_airtime(s)
   #duration is automatically overwritten by metadata fields passed in
   #with audio