Fixing handling of content node version lookup

Fixes https://www.pivotaltracker.com/story/show/80903880
Technically, the "auto-versioning" feature has been removed, i.e. versioning on every change. The automatic addition of the versioning-mixin when creating a new version may be called something like auto-mixin.
Suggestion: change test method name to "testDatastreamAutoMixin()"