void stop() {
      synchronized (this) {
        isStopped = true;
        notifyAll();
      }
      try {
        sweeperThread.join(100);
      } catch (InterruptedException ignore) {
        Thread.currentThread().interrupt();
      }
    }
For all tombstone this sweeper knows about call the predicate. If the predicate returns true
then remove the tombstone from any storage and update the memory estimate.

@return true if predicate ever returned true
geode-core/src/main/java/org/apache/geode/internal/cache/TombstoneService.java