Declare more framework non-const statics const or atomic

[wmtan]

This pull request is for thread safety in the framework. Some more non const statics that are never modified are declared const, snd some that are modified are declared std::atomic. One that is never read is removed.
Tested with checkdeps -a and the relval matrix.

[cmsbuild]

A new Pull Request was created by @wmtan for CMSSW_7_0_X.

Declare more framework non-const statics const or atomic

It involves the following packages:

FWCore/PluginManager
FWCore/Services
FWCore/Framework

@Dr15Jones, @ktf, @nclopezo can you please review it and eventually sign? Thanks.
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@ktf you are the release manager for this.

[Dr15Jones]

This variable should just be removed. It is set in three places but never read.

[cmsbuild]

Pull request #1296 was updated. @Dr15Jones, @ktf, @nclopezo 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 or unless it breaks tests. @ktf can you please take care of it?

[nclopezo]

+1
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/1163/summary.html