DAOS-VOL

Merge pull request #129 in HDF5VOL/daos-vol from ~NFORTNE2/daos-vol:async_link_obj to async_link_obj

* commit 'e7c43d49f4a6eed7d2915cbd1e34eaf229a01032':
  Remove unused function H5_daos_group_update_max_crt_order_key().  Add missing function description.
  Implement internally asynchronous group get info.  Other minor fixes.