TCPListener fix for #25

[soypat]

Attempting to fix bug in TCPListener, which leaks a connection on RST receive.

See #25

[codecov]

Codecov Report

Attention: Patch coverage is 56.25000% with 14 lines in your changes missing coverage. Please review.

Project coverage is 46.03%. Comparing base (1201bab) to head (66c9a7d).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
stacks/portstack.go	0.00%	9 Missing and 1 partial ⚠️
stacks/tcplistener.go	80.00%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #33      +/-   ##
==========================================
+ Coverage   45.99%   46.03%   +0.03%     
==========================================
  Files          29       29              
  Lines        4937     4946       +9     
==========================================
+ Hits         2271     2277       +6     
- Misses       2406     2410       +4     
+ Partials      260      259       -1     

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[soypat]

Not having much time to work on this right now.