Make HcalDDDGeometry thread-safe

[Dr15Jones]

Made caching of values internal to HcalDDDGeometry thread-safe. Given that the caching is done only once and kept for a long time and only one HcalDDDGeometry tends to be used at a time a std::mutex was used to synchronize the filling of the cache. This minimized the amount of code that had to be changed.

[Dr15Jones]

This is a bug fix since we already have stream based modules in CMSSW_7_1_X which use this object and therefore are not thread-safe without the fix.

[cmsbuild]

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

Make HcalDDDGeometry thread-safe

It involves the following packages:

Geometry/HcalTowerAlgo

@civanch, @Dr15Jones, @ianna, @mdhildreth, @cmsbuild, @nclopezo, @Degano, @ktf can you please review it and eventually sign? Thanks.
@ghellwig this is something you requested to watch as well.
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@nclopezo, @ktf you are the release manager for this.
You can merge this pull request by typing 'merge' in the first line of your comment.

[ianna]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_1_X IBs unless changes or unless it breaks tests. @nclopezo, @ktf can you please take care of it?

[cmsbuild]

+1
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4167/1670/summary.html

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_1_X IBs unless changes (tests are also fine). @nclopezo, @ktf can you please take care of it?