DAOS-VOL

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

* commit '443cd33bb5d35dab69d7a5ed8009a217f946fafb':
  Update submodules
  Update submodules for HDF5 reference fixes
  Update HDF5 submodule
  Implement H5VL_FILE_IS_EQUAL
  Fix more bugs in fillval implementation.
  Fix bugs in fillval implementation.
  RM trailing whitespace.
  Initial implementation of fill values.  Untested.