DAOS-VOL

Merging in latest from upstream (HDF5VOL/daos-vol:refs/heads/master)

* commit '4b4c5823e256c9101a131012c6702ecf205a3a32':
  Updates to user's guide for new H5A routines
  Ensure that object is a DAOS VOL object in H5Fget_obj_count/get_obj_ids
  Update VOL test submodule for h5_fileaccess fix
  Update HDF5 submodule for H5VL__new_vol_obj fix
  Update DAOS VOL for latest HDF5 changes
  Update VOL test submodule
  Fix issue with H5_daos_object_open and default LAPL
  Initial implementation for H5Aexists
  Add support for ACPL to attribute creation/opening/closing
  Add implementation for H5Fget_obj_ids
  Add implementation for H5Fget_obj_count
  Correctly handle the H5F_ACC_EXCL flag