Fix hang in SSL do_handshake and rework server shutdown routine

[uzlonewolf]

I was having a problem with the server hanging and not accepting new connections. I tracked it down to connections which have been opened but then do not complete a SSL/TLS handshake. It can be reproduced by simply opening a TCP connection and then not sending anything; example python:

~$ python3

Python 3.11.2 (main, May  2 2024, 11:59:08) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.

>>> import socket
>>> s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> s.connect(('MY IP', PORT))
>>> 

The server is now hung and no other connection can be opened.

Closes #13

I also reworked the server shutdown code so it actually sends the CLOSE command it queues up.

Closes #85