Clean up sessions/sockets if client does not send QUIT
Brought to you by:
chrismair
What if the client never sends the QUIT command, and we have a long-running server?
See:
https://sourceforge.net/p/mockftpserver/bugs/24/
In local testing, I see "java.lang.OutOfMemoryError: unable to create new native thread" after instantiating lots of local FTP clients.