Improve login performance by reducing PEP work
When a user logs in the PEP module executes a DB query for each contact that the user has in the roster. This is slowing down the login process and the entire server in general. Lets queue this work and be processed by another thread.
A further optimzation (if needed) could be to cache the "no PEP service" to prevent executing queries for users that do not have a PEP service.