vchoi_fork

[svn-r12811] Purpose:
Bug fix.

Description:
AIX complained if some files are still open when MPI_Finalize is called,
so code called _exit without calling MPI_Finalize.  But in Linux hosts
with MPICH, the MPI processes terminated but the launch processes got
stuck waiting for those processes to end properly and they would hang
on forever.  As more tests ran, more processes got stuck.

Solution:
In order to please both AIX and MPICH, the MPI file handles are retrieved
and closed outside of the HDF5 library, then call MPI_Finalize and then
_exit.

Tested:
in heping and copper.