Revert PFElecTkProducer to legacy module because of TMVA

[Dr15Jones]

The TMVA code is not thread safe so PFElecTkProducer which uses this
must be reverted back to a legacy module.

[cmsbuild]

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

Revert PFElecTkProducer to legacy module because of TMVA

It involves the following packages:

RecoParticleFlow/PFTracking

@nclopezo, @cmsbuild, @anton-a, @thspeer, @slava77, @Degano can you please review it and eventually sign? Thanks.
@bachtis, @lgray 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.
You can reject by replying to this message having '-1' in the first line of your reply.
@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.

[cmsbuild]

-1
When I ran the RelVals I found an error in the following worklfows:
4.22 step2

runTheMatrix-results/4.22_RunCosmics2011A+RunCosmics2011A+RECOCOSD+ALCACOSD+SKIMCOSD+HARVESTDC/step2_RunCosmics2011A+RunCosmics2011A+RECOCOSD+ALCACOSD+SKIMCOSD+HARVESTDC.log

you can see the results of the tests here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3918/1562/summary.html

[cmsbuild]

+1
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3918/1567/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3918/1567/summary.html

[Dr15Jones]

The test failure was from an unrelated DAS failure. @nclopezo please re run.

[cmsbuild]

+1
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3918/1568/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3918/1568/summary.html

[slava77]

+1

for #3918 59eefd2
jenkins OK

[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?