Thread safety cleanup in Geometry

[wddgit]

Make the return value of a function be
a const ref instead of just a ref.
Eliminates a potential thread safety problem
reported by the clang static code analyzer.

[cmsbuild]

A new Pull Request was created by @wddgit (W. David Dagenhart) for CMSSW_7_1_X.

Thread safety cleanup in Geometry

It involves the following packages:

Geometry/TrackerGeometryBuilder

@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.
You can sign-off by replying to this message having '+1' in the first line of your reply.
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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-3307/879/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?

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3307/879/summary.html