message: Fix sidre_createdatastore example so that it's treated as a parallel
  test when MPI is available.
diff: set(example_sources
  sidre_stressgroups.cpp
  sidre_shocktube.cpp
  - sidre_createdatastore.cpp
  )
  +if(ENABLE_MPI)
  + set (example_parallel_sources
  + sidre_createdatastore.cpp)
  +else()
  + list(APPEND example_sources sidre_createdatastore.cpp)
  +endif()
  set(F_example_sources
  sidre_shocktube_F.f
  @@ -63,6 +68,23 @@ foreach(example_source ${example_sources})
  COMMAND ${exe_name}_ex )
  endforeach()
  +if(ENABLE_MPI)
  + foreach(example_source ${example_parallel_sources})
  + get_filename_component(exe_name ${example_source} NAME_WE)
  + blt_add_executable(
  + NAME ${exe_name}_ex
  + SOURCES ${example_source}
  + OUTPUT_DIR ${EXAMPLE_OUTPUT_DIRECTORY}
  + DEPENDS_ON ${sidre_example_depends} ${EXTRA_LIBS}
  + FOLDER axom/sidre/examples)
  +
  + blt_add_test( NAME ${exe_name}
  + COMMAND ${exe_name}_ex
  + NUM_MPI_TASKS 1
  + )
  + endforeach()
  +endif()
  +
  if(ENABLE_FORTRAN)
  foreach(example_source ${F_example_sources})
  get_filename_component(exe_name ${example_source} NAME_WE)
  