hdf5_ep

[svn-r6046] Purpose:
    Improvement
Description:
    fillval will fail to find the pre-exist data file if it is run
    in --srcdir mode without setting $srcdir properly.  This is
    setup properly in the Makefile but unsuspecting users trying just
    ./fillval were puzzled by the failure.
Solution:
    put in a more descriptive error message with a possible remedy.
Platforms tested:
    Modi4 only since this is just adding a printf statment.