@Override
  public void close() throws IOException {
    if (manageConnection && this.connection != null && !this.connection.isClosed()) {
      this.connection.close();
    }
  }
Creates AggregationClient with internally managed Connection, which will be used by methods
taking a {@link TableName} to create the necessary {@link Table} for the call. The Connection
will immediately be created will be closed when {@link #close()} is called. It's important to
call {@link #close()} when done with this AggregationClient and to otherwise treat it as a
shared Singleton.
@param cfg Configuration to use to create connection
hbase-endpoint/src/main/java/org/apache/hadoop/hbase/client/coprocessor/AggregationClient.java