media: Refine the idle state management in the EOS callback
media: Refine the idle state management in the EOS callback

So we don't show a black frame when looping the video.

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=657773

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