Send DeleteUsers/DeleteAllUsers to Trusty

Actually route the DeleteUsers/DeleteAllUsers calls to Trusty,
instead of immediately returning ERROR_NOT_IMPLEMENTED.

Bug: 160731903
Test: "atest VtsHalGatekeeperV1_0TargetTest"
      manual testing with added instrumentation
Change-Id: I11fdaa0812fdfbc9b926611b15d84513ab13b18e