[lastfm] Remove the gconf notify hooks when disposing the backend
[lastfm] Remove the gconf notify hooks when disposing the backend

We can't just remove the directory as we would normally since we may be given
back the same gconf client object in a future instance and would then end up
with duplicate notifications.

lcp/libsocialweb,GNOME/libsocialweb,ThomasBollmeier/libsocialweb-flickr-oauth,ThomasBollmeier/libsocialweb-flickr-oauth,lcp/libsocialweb,lcp/mojito,ThomasBollmeier/libsocialweb-flickr-oauth,lcp/libsocialweb,lcp/mojito,GNOME/libsocialweb,lcp/mojito,GNOME/libsocialweb