Namespace scope events in storage

Due to a bug, all events in etcd were going into the same etcd directory.

This change will scope events properly to a namespace like all other objects.

If you update a Kubernetes cluster that had populated events, this change will make the events no longer appear to the end-user.  Given that events had a TTL of 2 days by default, I am not sure how big of a deal that is to preserve the data versus state on the upgrade that cluster users will expire existing events.

@lavalamp - this is the fix per our previous discussion