hdf5_msb

[svn-r17832] Bug fix:(sort of)
Some systems, like AIX poe, interpret exit(134) the same as if the process has
really been interrupted by the abort signal and prints extra messages that
confuse test script which is looking for matching output.

Solution:
Changed it to exit(6) which still has the "appearance" of an abort signal which
carries the value of 6 in Unix systems.

Tested: LLNL Up both serial and Parallel.