fix: HA proxy memory runaway on certain rpm based distro's -> Setting maxconn in haproxy config (#15319)

[timgriffiths]

Fixes #15319

I propose the best way to fix this issue is by setting a global setting in haproxy config maxconn 4000 you can also fix it by changing the max open file limit in containerd but as this comment points out docker-library/haproxy#194 (comment) this only works as haproxy derives the max number of connections from the max open files on a system which seems like a bit of a bug or at least we should set a max as part of the config.

Setting the default sufficiently large so that this should not be a problem. this could be backported to whichever versions users need as it's a simple haproxy config tweak

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.94%. Comparing base (8a28279) to head (c6d8731).

Additional details and impacted files

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##           master   #18283   +/-   ##
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  Coverage   44.94%   44.94%           
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  Files         354      354           
  Lines       47740    47740           
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  Hits        21455    21455           
  Misses      23482    23482           
  Partials     2803     2803           

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