Fix parallel bug in DataWriterHDF5Ext (ISGetSize -> ISGetLocalSize).
Merge branch 'knepley/upgrade-petsc-interface' of github.com:geodynamics/pylith into knepley/upgrade-petsc-interface

* 'knepley/upgrade-petsc-interface' of github.com:geodynamics/pylith:
  HDF5: Must use local IS size when accessing indices