handling of ...v1/DQMIO, ...v2/DQMIO

[franzoni]

Example of a workflow which was run more than once by ops and more than once has sent harvested DQM to the relval gui:

https://cmsweb.cern.ch/reqmgr/reqMgr/outputDatasetsByRequestName/heli_RVCMSSW_7_4_3ADDMonoJet_d3MD3_13_150527_011352_1952
= > has yielded
/RelValADDMonoJet_d3MD3_13/CMSSW_7_4_3-MCRUN2_74_V9-v1/DQMIO
/RelValADDMonoJet_d3MD3_13/CMSSW_7_4_3-MCRUN2_74_V9-v9/DQMIO

The logical thing here would be, for two files found with the same DS name except v1,v9, to only consider the instance with the largest version number