Use new return value from FPE

This is a fix for the unit test for floating point exceptions in the ROOT 6 IB.  The return code from cmsRun when a floating point exception is thrown has changed between ROOT 5 and ROOT 6.  This is not fully understood, but is likely due tot eh ROOT signal handler, which cmsRun uses.  Since the previous return code in the test was empirically determined, we simply empirically determine the new return code and change it in the test script.

Please merge this promptly unless there are issues.