ngrenz small optimization of Tracker Hit Associator

[ngrenz]

Additional and last changes in TrackerHitAssociator which are PR of a work intended to optimize gradually the performance of tracker validation code.
Any comments and suggestions are welcome.

Outputs are supposed to be unchanged.

[ngrenz]

@boudoul FYI

[cmsbuild]

A new Pull Request was created by @ngrenz for CMSSW_7_6_X.

ngrenz small optimization of Tracker Hit Associator

It involves the following packages:

SimTracker/TrackerHitAssociation

@cmsbuild, @civanch, @mdhildreth can you please review it and eventually sign? Thanks.
@makortel, @GiacomoSguazzoni, @rovere, @VinInn, @wmtford, @cerati, @threus, @dgulhan 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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@Degano you are the release manager for this.
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[civanch]

please test

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

+1
Tested at: 279a6e1
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-10346/8908/summary.html

[civanch]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_6_X IBs (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @smuzaffar

[davidlange6]

+1