m_kicknorejoin Minor improvements

- Ignore remote users
- Remove expired items in one pass
m_kicknorejoin Limit time to 30m by default

In the current implementation we only expire entries when someone joins, without a limit it was possible to make us practically never remove entries and consume (a tiny amount of) memory for each entry until the mode was removed/parameter was changed

The default limit of 30m is chosen to not surprise people when they upgrade. If you need to prevent rejoins for more than a minute then you should set a (timed)ban instead

Config option is available to change the limit (2.0 only)
m_kicknorejoin Store and compare uuids instead pointers

Fixes the off chance scenario where we disallow a join because a previously kicked user has quit and the User who is trying to join happens to be allocated at the exact same memory location