tests: dump logs at the end of exit callback

[algorandskiy]

Summary

There are some random TestCatchupOverGossip failures like this , and the panic itself is caused by the fact controller's StartAlgod inner goroutine calls asserts after the test itself is terminated. For some reason we do not get any log output in case of panic and my current suggestion it is because of STDOUT buffering and panic just flushes STDERR with its own message.
This PR does not prevent the race itself but makes it much less probable by deferring logs dumping to after asserting.

A proper fix is somewhat complicated because the controller object copying/modifying, and StartAlgod is called on a different object than StopAlgod. I suggest to apply this fast fix to see if it help gathering required info, and implement the controller lifetime refactoring if needed.

Test Plan

This is a test fix.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.75%. Comparing base (13e66ff) to head (9b7b3e6).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5952      +/-   ##
==========================================
+ Coverage   55.71%   55.75%   +0.03%     
==========================================
  Files         489      489              
  Lines       68111    68111              
==========================================
+ Hits        37950    37972      +22     
+ Misses      27586    27568      -18     
+ Partials     2575     2571       -4     

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