Fix assert_script_sudo and script_sudo being called as root
Found working on: #43703
assert_script_sudo as root (eg to avoid code duplication) it fails as openQA expects a password prompt that doesn't appear when the shell is already a root-shell:
To show this issue I just added this two lines to the top of a test module:
select_console 'root-console'; assert_script_sudo 'whoami';
Expected result: openQA should gracefully handle this.
- AC1: assert_script_sudo can be run when current user is root.
- AC2: Duplicate code is adapted (like https://github.com/os-autoinst/os-autoinst-distri-opensuse/pull/6270)