default AsyncAdmin getAdmin(ExecutorService pool) {
    return getAdminBuilder(pool).build();
  }
Retrieve an {@link AsyncAdmin} implementation to administer an HBase cluster.
<p>
The returned instance will use default configs. Use {@link #getAdminBuilder(ExecutorService)}
if you want to customize some configs.
@param pool the thread pool to use for executing callback
@return an {@link AsyncAdmin} instance for cluster administration
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncConnection.java