getParameterNames is really a const function

[wmtan]

I happened to notice that both functions in the ParameterSet::getParameterSetNames overload set are really const functions, but only one of them has const in its signature. This simple pull request adds const to the signature of the other function, which should also have it. This makes one fewer non-const function of class ParameterSet.

[cmsbuild]

The following categories have been signed by chrjones (a.k.a. @Dr15Jones on GitHub): Core

@cms-git-visualization, @cms-git-core, @cms-git-geometry

[ktf]

Actually this kills the build:

https://cmssdt.cern.ch/SDT/cgi-bin/buildlogs/slc5_amd64_gcc472/CMSSW_7_0_X_2013-08-04-0200/IOPool/Common
https://cmssdt.cern.ch/SDT/cgi-bin/buildlogs/slc5_amd64_gcc472/CMSSW_7_0_X_2013-08-04-0200/PhysicsTools/UtilAlgos
https://cmssdt.cern.ch/SDT/cgi-bin/buildlogs/slc5_amd64_gcc472/CMSSW_7_0_X_2013-08-04-0200/RecoTracker/TkNavigation

Given there are only three places where this is used, maybe it's better to kill the API completely and have two calls to the one which has allows specifying trickiness?

[ktf]

Or even better make trackiness an enum {Tracked, Untracked, Any} and use that instead of the bool?

[wmtan]

This change was resubmitted in a different pull request that removes the function ambiguity and does not cause these build errors.