Delay user state deletion in AppOpsService

Some other services may still be working or trying to start new work for
the removed user as a response to the user being removed. We can hold
onto the state for a bit longer so that we don't see denials that look
unexpected.

Test: Remove a user
Bug: 377781062
Flag: EXEMPT bugfix
Change-Id: Ie3bdb44b31090d91049081c01ed7aca7e8ba7cb1