Fix race condition during ssh session probe

[giffels]

Fixes #369.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.94%. Comparing base (58b66e0) to head (7428199).
Report is 11 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #370   +/-   ##
=======================================
  Coverage   98.94%   98.94%           
=======================================
  Files          55       55           
  Lines        2266     2270    +4     
=======================================
+ Hits         2242     2246    +4     
  Misses         24       24           

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[maxfischer2781]

I think this has a race condition where the new connection already exists but the old bound is still there. (Which is a race we had before, too. 😬 )

There are some tagalong change to my recommended fix, I'll try and create a PR for all that this evening.

[giffels]

Superseded by #371.