Are you supposed to put a vapor barrier on both sides of the common garage wall (wall between garage and house)?
If you are insulating the walls with a Kraft Faced insulation then the paper side needs to be against the house wall.  Regardless of any other insulation anywhere else in the garage, paper to the warm side always.  If you are using unfaced insulation, then you probably won't get the vapor barrier you want and need unless you use foam board or closed cell spray foam.  Putting the vapor barrier on the outside will cause condensation in your wall.