CMS - build record for the pileup dataset

[katilp]

Build a record for the pileup dataset /Neutrino_E-10_gun/RunIISummer20ULPrePremix-UL16_106X_mcRun2_asymptotic_v13-v1/PREMIX

/Neutrino_E-10_gun/RunIISummer20ULPrePremix-UL16_106X_mcRun2_asymptotic_v13-v1/PREMIX

The previous pileup dataset records were GEN-SIM, this is now different: PREMIX

A new json file: cms-simulated-datasets-2016-pileup.json
See https://github.com/cernopendata/opendata.cern.ch/blob/master/cernopendata/modules/fixtures/data/records/cms-simulated-datasets-2015-pileup.json

recid: 30566

[katilp]

Fix in the same go 2016 -> 2015 in https://github.com/cernopendata/opendata.cern.ch/blob/master/cernopendata/modules/fixtures/data/records/cms-simulated-datasets-2015-pileup.json#L275-L276