The `| tee` invocation always masked the return value of the
switch-to-configuration test.
```
~ $ false | tee && echo "oh no"
oh no
```
The added wrapper script will still output everything to stderr, while
passing failures to the test harness.
Fixes#28443
Fixed few invocations to `systemctl` to have an absolute path. Additionally add
LOCALE_ARCHIVE so that perl stops spewing warning messages.
