[test] Added fixes for FEC test occasional failure

[ethouris]

This adds fixes:

1. Extended timeout for srt_accept_bond call to 2 seconds.
2. Preinitialized buffers for extracted FEC configuration (happened to be displayed with garbage contents)
3. Made the accept failure assert instead of expect (failure will only lead to other failures).

[codecov-commenter]

Codecov Report

Merging #2037 (36b1d77) into master (5205c3c) will decrease coverage by 0.11%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2037      +/-   ##
==========================================
- Coverage   63.74%   63.63%   -0.12%     
==========================================
  Files          89       89              
  Lines       18954    18968      +14     
==========================================
- Hits        12083    12071      -12     
- Misses       6871     6897      +26     

Impacted Files	Coverage Δ
test/test_fec_rebuilding.cpp	100.00% <100.00%> (ø)
srtcore/list.cpp	76.33% <0.00%> (-5.36%)	⬇️
srtcore/core.h	79.26% <0.00%> (-3.66%)	⬇️
srtcore/window.h	96.72% <0.00%> (-3.28%)	⬇️
test/test_bonding.cpp	97.84% <0.00%> (-0.54%)	⬇️
srtcore/core.cpp	58.31% <0.00%> (-0.27%)	⬇️
srtcore/api.cpp	51.60% <0.00%> (+0.05%)	⬆️
srtcore/queue.cpp	81.28% <0.00%> (+0.58%)	⬆️
srtcore/congctl.cpp	82.81% <0.00%> (+2.08%)	⬆️
srtcore/cache.h	83.07% <0.00%> (+3.07%)	⬆️

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