cmsRun returns non-zero if caught unix signal

If any of the signals cmsRun catches (SIGINT and SIGUSR2) are caught, cmsRun now returns a non zero value. This was requested by data ops.
Backported from CMSSW_7_0_X.

Conflicts:
	FWCore/Framework/bin/cmsRun.cpp
Merge pull request #1540 from Dr15Jones/cmsRunReturnNoneroOnSignalFor6_2_X

cmsRun returns non-zero if caught unix signal