Skip main user designation/creation when booting to HSU on provisioned devices.

When the HSUM device is provisioned, it's expected that it will boot in system used. I use the `config_hsumBootStrategy` flag as it specifies
the boot strategy and avoid creating an initial admin user.

Bug: 374926694
Flag: EXEMPT new code protected by new config that is enabled only for desktop
Test: manually build and deploy in DUT and test both cases
Change-Id: Iff76a8b7ab400962676ebe32dcb966e53272fddb