Merged requested to merge oabouzei/athena:21.2-STUpdates-12.03.2019 into 21.2
Update of trig uncertainties: Previously, this was not done, resulting in the systematics for electron single lepton triggers not having the proper systematics applied in some cases. Adding this to the systematics classification should fix the issue.
Updates for pileup autoconfig: EL jobs no longer have metadata access during initialize. For the time being, a new property has been added for users to specify the mcChannel number manually of their samples to get around this. Appropriate ART tests have also been updated.