Make cache of TriggerNames thread-safe

[Dr15Jones]

Changed to a thread safe container for the static cache of TriggerNames.

[cmsbuild]

A new Pull Request was created by @Dr15Jones (Chris Jones) for CMSSW_7_1_X.

Make cache of TriggerNames thread-safe

It involves the following packages:

FWCore/Common

@cmsbuild, @Degano, @Dr15Jones, @ktf, @nclopezo can you please review it and eventually sign? Thanks.
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[Dr15Jones]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IBs unless changes or unless it breaks tests.

[cmsbuild]

+1
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-2071/1/summary.html

[cmsbuild]

Pull request #2071 was updated. @Dr15Jones, @ktf can you please check and sign again.

[Dr15Jones]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IBs unless changes (tests are also fine).