protected boolean checkPrevAcks() {
    // ARB: Implemented in DurableHARegionQueue.
    return true;
  }
For non blocking queue , this method either returns null or an Object. For blocking queue it
will always return with an Object or wait for queue to be populated.

@throws CacheException The exception can be thrown by BlockingQueue if it encounters
        InterruptedException while waiting for data
geode-core/src/main/java/org/apache/geode/internal/cache/ha/HARegionQueue.java