Revert "Merge pull request #3836 from leggat/threadSafe"

This reverts commit f971fa94012da2ca5eb775b247ad68067bfe4d3f, reversing
changes made to 406887d31219df1273fef9fe30e076572cc721a9.
Merge pull request #3902 from ktf/revert-3836

Revert "Merge pull request #3836 from leggat/threadSafe"
Merge remote branch 'origin/CMSSW_7_1_X' into CMSSW_7_0_X