@Override
    public ClientProtos.ScanResponse scan(final RpcController controller,
      final ClientProtos.ScanRequest request) throws ServiceException {
      exceptions.throwOnScan(this, request);
      return super.scan(controller, request);
    }
Test that our cleanOverlappingRegions doesn't incorrectly remove regions from cache. Originally
encountered when using floorEntry rather than lowerEntry.
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestMetaCache.java