hdf5_ep

[svn-r18985] Test feature: (bugs 1919)

Problem: some launching command like yod (and sometimes mpirun), do not pass
back the exit code of the executables back to the shell. It always returns 0
if it can launch the executable. This cause tests that expect non-zero exit
code to fail incorrectly.

Short term Solution:
Added the feature that if $RUNSERIAL_NOEXITCODE is defined, do not
test conditions that rely on non-zero exit code.

Tests:
dove-linux using RUNSERIAL=thgyod to see the failures and using
$RUNSERIAL_NOEXITCODE=yes to bypass the errors.
Also h5committested.