Players who cannot connect to the server should not affect it's performance, even when spamming with failed login tries.

Players who for any reason (auth servers or session servers down, ban, not on whitelist, having client side issues) cannot log in and still tries to do so repeatedly causes a server crash.

To reproduce:
1 Create a server
2 Turn on whitelist
3 Make sure you're not on whitelist
4 Repeatedly and rapidly try to connect to the server
5 After 5-15 failed logins the server should crash.

First I am sorry for posting yet another duplicate, but if this is not correctly identified and makes it to full release and gets known to the public there will be outrage since every banned kid will crash the server they were banned from. The problem is already big enough for me to not be able to continue using 14w07a on my server to help identify other bugs.

I originally posted my findings in MC-48489 which was later categorized as a duplicate of MC-48411 which erroneously identifies slime blocks as causing the crashes and of course has not been confirmed, since slime blocks seem to work just fine on servers except for the shadow.