Test that the password isn't truncated (again)

Test that Gatekeeper doesn't truncate passwords, either due to them
containing NUL bytes or being long.

This is https://r.android.com/2151558 ported to the AIDL test.  Even
though the AIDL test wasn't added until after my change, it was forked
from an earlier version of the HIDL test that didn't have my change.

Bug: 238919794
Test: atest VtsHalGatekeeperTargetTest # on Cuttlefish
Change-Id: I6fec951e67a35d5275a67244fbef07d1435c9f4f