Add some small fixes to the MQAC local exploit

* Check for `INVALID_HANDLE_VALUE` when attempting to open the
  device, as this is what is returned when the device doesn't exist.
* Make sure that we only run the exploit against tartgets that we
  support directly to make sure we don't BSOD machines (such as what
  happens with SP1/SP2).
* Add a call to `check` in the exploit code.