EvF lumiblock consistency cross-check (backport of #4399)

Hi,
this resolves a very recently found issue in DAQ where there is a problem in input discovery that might cause events being processed assuming wrong lumisection number. I am also posting to  cms-release-dataops egroup to inform about this. Please merge for 7_1_1 if possible.

*revert removing check for json file after EoLS has appeared
*check that LS is consistent with the one coming from information shared among multiple CMSSW processes
*add several info logs to verify what was written in the lock file