Guard the nPho histograms from double counting, should fix HI issues

In HI reco DQM, photons are being double-counted because in HI RECO we do not pre-select at the RECO level for isolated photons. Since most HI photons are not isolated according to the default cuts they have type==0 and get double-counted.

Forward port of #6574 into CMSSW_7_4_X. Will merge automatically since the former is fully signed in CMSSW_7_3_X.