Implemented CREATE_USER and REMOVE_USER on VHAL reference implementation.

Test: adb shell lshal debug android.hardware.automotive.vehicle@2.0::IVehicle/default --set 299896585 a 1 i 666 i 1 && \
      adb shell lshal debug android.hardware.automotive.vehicle@2.0::IVehicle/default --user-hal

Bug: 150408921
Bug: 150409600

Change-Id: If971c262ecaba604f55582b3ef0a850410d82ff9
3 files changed