Fixed screwup with VP-X switch signal grounds

Most of the loads on the load shed circuit are shed via software when
the EL+L/Load Shed switch is pressed...however, as the schematic was
written, anything with its own switch (strobes, nav lights, landing
lights, and pitot heat) would override the load shed switch.

Therefore, the ground path for those switches has to go through the load
shed switch.  That way, if you hit that switch, it instantly kills
everything non-essential.  Procedure to turn those devices back on is
the same for everything else that's automatically shed (via EFIS menu).