[ENGOPS-561]: Setting hdp20 version to 5.0.4 for upcoming release

This would then require a new version property added to the global properties list the we use on release and a new version merger deployment. Plus introduces the possibility of build accidentally overriding the required version for the release. I would prefer that this stayed in dev's hands since they are expected to be in tune with the big-data release. Otherwise a lack of communication from PM->Dev-> build on any given maint release will break us.