Setting/Updating Cron settings is broken in 0.11

When trying to change or set the cron settings for any notebook, the server will show the error

java.lang.String cannot be cast to java.util.Set

The underlying error is, that the frontend sends the roles as an escaped String but the 
‎NotebookService::updateNote Method expects a JSON Array in Line 902:
 

          Set<String> requestCronRoles = (Set<String>) config.get("cronExecutingRoles");
 

As a result the update will error.
 
This is a regression as 0.10 did not show this errornous behaviour