vino: use wrapGAppsHook

Fixes this:

  .vino-server-wr[8931]: Using the 'memory' GSettings backend. \
  Your settings will not be saved or shared with other applications.

Still, the screen sharing settings under "gnome-control-center sharing"
does not seem to be persisted (except the enabling/disabling sharing
flag itself). Making changes and then re-opening gnome-control-center
shows the default screen sharing settings. Sigh.