add copyMVA parameter in order to handle also track collections not associated to any MVA value map (i.e., some track collection used @HLT)
Merge pull request #6538 from mtosi/from-CMSSW_7_2_1_fixTrackListMerger

Add copyMVA parameter in MultiTrackMerger (backport https://github.com/cms-sw/cmssw/pull/6535)