PropertiesUtil-related test failures

See example failed run in CI: https://github.com/apache/logging-log4j2/runs/6619223440?check_suite_focus=true and https://github.com/apache/logging-log4j2/runs/6619473745?check_suite_focus=true

Each test relies on setting a system property before PropertiesUtil should be referenced, but some strange behavior is causing this not to work in CI.