GlobalTag*.py: sort the additional payloads

Sort the additional payloads from release-level or user-level customisations to the global tags,
to ensure a consistent hash of the process configuration.
Merge pull request #4729 from fwyzard/GlobalTag_fixed_order_72X

GlobalTag*.py: sort the additional payloads
Merge remote branch 'origin/CMSSW_7_2_X' into CMSSW_7_0_X