stream_filter: improve parenting

Attach to the source stream´s parent rather than the source stream.
This avoids recursive vlc_object_release() when deleting the chain.

src/input/stream_filter.c

@@ -42,7 +42,7 @@ stream_t *stream_FilterNew( stream_t *p_source,
     stream_t *s;
     assert( p_source != NULL );
 
-    s = stream_CommonNew( VLC_OBJECT( p_source ) );
+    s = stream_CommonNew( p_source->p_parent );
     if( s == NULL )
         return NULL;