default void postListNamespaceDescriptors(ObserverContext<MasterCoprocessorEnvironment> ctx,
    List<NamespaceDescriptor> descriptors) throws IOException {
  }
Called after a listNamespaceDescriptors request has been processed.
@param ctx         the environment to interact with the framework and master
@param descriptors the list of descriptors about to be returned
hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/MasterObserver.java