Fix miniAOD validation for MET : 75X

[mmarionncern]

Following the issue of workflow 11325 noticed after the integration of #9117 , this PR contains the corresponding fix.
Also fixed the remaining GetBylabel functions in the met correction tool.

@davidlange6

[cmsbuild]

A new Pull Request was created by @mmarionncern for CMSSW_7_5_X.

Fix miniAOD validation for MET : 75X

It involves the following packages:

Configuration/StandardSequences
JetMETCorrections/Type1MET

@cmsbuild, @vadler, @franzoni, @davidlange6, @monttj can you please review it and eventually sign? Thanks.
@ghellwig, @TaiSakuma, @jdolen, @makortel, @GiacomoSguazzoni, @rappoccio, @rovere, @VinInn, @Martin-Grunewald, @ahinzmann, @nhanvtran, @schoef, @cerati, @mariadalfonso, @dgulhan this is something you requested to watch as well.
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[monttj]

please test

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

+1
Tested at: 27969b7
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-10019/188469/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-10019/188469/summary.html