Fix issue 1279: getByToken implementation reveal a problem due to importing the code to book histograms to the beginRun.
Merge pull request #1297 from acaudron/getByTokenDQMbtag

DQM fix -- Fix issue #1279 related to consumes migration for BTag DQM.
Merge remote-tracking branch 'origin/CMSSW_7_0_X' into CMSSW_7_0_X