@Override
  public long cacheTimeMillis() {
    if (system != null) {
      return system.getClock().cacheTimeMillis();
    }
    return System.currentTimeMillis();
  }
Used by unit tests to allow them to change the default disk store name.
geode-core/src/main/java/org/apache/geode/internal/cache/GemFireCacheImpl.java