Made statics into atomics in CSCALCTTrailer

Changed statics to atomics becuase helgrind was reporting thread
safety issues.
NOTE: It would be much better if firmwareVersion was made a regular
member data instead of a static. When we are processing multiple
runs simultaneously we may need more than one value in the job.
Merge pull request #3876 from Dr15Jones/makeStaticAtomicCSCALCTTrailer

Made statics into atomics in CSCALCTTrailer
Merge remote branch 'origin/CMSSW_7_1_X' into CMSSW_7_0_X