[audio] Fix the :progress property getter
[audio] Fix the :progress property getter

The ClutterMedia:progress property is a double, not an integer.

GNOME/clutter-gst,GNOME/clutter-gst,lubosz/clutter-gst,ystreet/clutter-gst,lubosz/clutter-gst,GNOME/clutter-gst,ystreet/clutter-gst,skinkie/clutter-gst,skinkie/clutter-gst,ystreet/clutter-gst,ystreet/clutter-gst,lubosz/clutter-gst,skinkie/clutter-gst,GNOME/clutter-gst