@Override
      public ColumnFamilyDescriptorBuilder bulkFamily(byte[] familyName) {
        ColumnFamilyDescriptorBuilder builder =
          ColumnFamilyDescriptorBuilder.newBuilder(familyName);
        familyBuilders.add(builder);
        return builder;
      }
If the table is created for the first time, then "completebulkload" reads the files twice. More
modifications necessary if we want to avoid doing it.
hbase-server/src/main/java/org/apache/hadoop/hbase/tool/BulkLoadHFilesTool.java