Rectify unsupported configuration in bootloader settings when migrating from 15sp4 hpc
When migrating form 15sp4 hpc to 15sp5, the test encounters an unsupported bootloader configuration (unkown udev device), as seen here. The issue is likely caused by an earlier configuration which would need to be mitigated.
Migration: HPC https://openqa.suse.de/tests/9426332#step/start_install/2
AC1: Adjust the test so that bootloader configuration is written to an existing disk.