fix unrunable schedule
Check for unschedule attribute only, if available.
Merge pull request #3927 from lveldere/fastsim-fix-unrunnableschedule-genparticles

FastSim -- Fix unrunable schedule
Merge pull request #3929 from vadler/71X-fixMetUncertaintyToolsScheduled

AT -- Fix `metUncertaintyTools` for scheduled processing
Merge remote branch 'origin/CMSSW_7_1_X' into CMSSW_7_0_X