h5_test/run_par_test.sh should be converted to run_par_test.sh.in, and mpiexec replaced with @MPIEXEC@

[edwardhartnett]

The user can select at configure time a different parallel program launcher to use (default is 'mpiexec').

Parallel I/O tests are always run from test scripts, and to accommodate user selection of launcher, we now have things like nc_test4/run_par_test.sh.in, which gets converted to run_par_test.sh at configure time.

However, this has not been done for h5_test/run_par_test.sh. It needs to be.

[edwardhartnett]

Also it turns out that this test is not being run for the cmake build. I will add it.

ALso, also there is some part of the test that is commented out, but should not be. I've uncommented it.