Fix HLT rate plots in GeneralHLTOffline.cc
Make cache of TriggerNames thread-safe

Changed to a thread safe container for the static cache of TriggerNames.
Merge branch 'CMSSW_7_1_X' of https://github.com/cms-sw/cmssw into makeStaticThreadSafeInEventBase
Merge pull request #2070 from puigh/my-dqmoffline-hlt-rate-histo-fix

DQM fixes -- Fix HLT rate plots in GeneralHLTOffline.cc
Merge pull request #2071 from Dr15Jones/makeStaticThreadSafeInEventBase

Multithreading fixes -- Make cache of TriggerNames thread-safe
Merge remote branch 'origin/CMSSW_7_1_X' into CMSSW_7_0_X