reenable DQM harvesting for PromptReco

Due to some code restructuring in WMCore StdBase and PromptReco specs,
DQM harvesting is now off by default for all PromptReco workflows.
Reenable it.
Merge pull request #4056 from hufnagel/promptreco-harvest

reenable DQM harvesting for PromptReco