refactoring; improve diagnostic in fork-bomb test
refactoring; improve diagnostic in fork-bomb test

cyber-dojo/runner,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless