public void start() {
    synchronized (this) {
      stdout.start();
      stderr.start();
      started = true;
    }
  }
Starts the stdout and stderr reader threads for a running process. Provides a mechanism to
waitFor the process to terminate.
<p>
Extracted from ProcessWrapper.
geode-junit/src/main/java/org/apache/geode/test/process/ProcessOutputReader.java