text: Title: Events API returns raw etcd errors in some cases
  Body: The events REST storage object is not using generic.Etcd, and it's not wrapping the returned errors from etcd with the appropriate `pkg/api/errors/etcd` handles.  As a result, we return raw etcd errors to clients which leaks server information (security) and is also ugly.
  
  Spawned from https://github.com/openshift/origin/issues/3196
  