hdf5_msb

Merge pull request #2819 in HDFFV/hdf5 from coll_chunk_fill_fix to develop

* commit '4c43ff0b8b015ccfc1f4aeab18f189d629a5beb9':
  Simplify default use of MPI_BYTE
  Don't free builtin MPI_BYTE MPI type
  Simplify code to avoid using a boolean to free MPI types
  Avoid creating MPI datatypes on ranks with 0 chunks to write'