cache user ids for users with disabled accounts

@ormsbee , not sure if this is the right idea. I noticed that the UserStanding table was taking up a lot of db time, which is ridiculous seeing how small of a table it is. I thought caching its relevant content might speed up our response time. 

See:
https://rpm.newrelic.com/accounts/88178/applications/3343327/databases#id=407521706