private void testHookIfIdleExpireBatch() {
      if (IDLE_EXPIRATION && sleepTime >= EXPIRY_TIME && !expiredTombstones.isEmpty()) {
        expireBatch();
      }
    }
Returns true if keys needs to be tracked for clients registering interests on PR.
geode-core/src/main/java/org/apache/geode/internal/cache/TombstoneService.java