LockSettingsService: always get user properties from UserManagerInternal

UserManagerInternal is the preferred way to get user properties in
system_server itself, since it avoids unnecessary checks and an
unnecessary copy of the UserProperties object.

Bug: 403355811
Test: atest FrameworksServicesTests:com.android.server.locksettings
Flag: EXEMPT refactor
Change-Id: If83c4ee8a1624424ebd2a05b8385bb0c728727da