Make isUsingUnifiedPassword throw when used on parent instance

It doesn't make sense to call it via parent instance.

Bug: 70788883
Test: cts-tradefed run cts -m DevicePolicyManager -t com.android.cts.devicepolicy.ManagedProfileTest#testParentProfileApiDisabled
Change-Id: I66334757ca8e9ee2525dbe88c83216563837aee6
1 file changed