Add TerminalConsole test_without_start_listening

[cclauss]

Class variables should always be initialized in the .__init__() method but TerminalConsole.port is not. As discussed in:

• error at telnet shutdown in Python 3 #2702
• Define TelnetConsole.port = None in __init__() #2892

[codecov]

Codecov Report

Merging #6224 (cd9b51d) into master (c5fdba9) will increase coverage by 0.01%.
Report is 5 commits behind head on master.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6224      +/-   ##
==========================================
+ Coverage   88.59%   88.61%   +0.01%     
==========================================
  Files         161      161              
  Lines       11761    11775      +14     
  Branches     1907     1908       +1     
==========================================
+ Hits        10420    10434      +14     
  Misses       1011     1011              
  Partials      330      330              

see 1 file with indirect coverage changes

[wRAR]

Is this a work in progress?

[cclauss]

builtins.AttributeError: 'TelnetConsole' object has no attribute 'port'