Thread safety fix for PolyFit2DParametrizedMagneticField.cc
Merge pull request #1498 from smuzaffar/thread-safety-fix-PolyFit2DParametrizedMagneticField

Multithreading fixes -- Thread safety fix for PolyFit2DParametrizedMagneticField.cc
Merge remote-tracking branch 'origin/CMSSW_7_0_X' into CMSSW_7_0_X