Fix race condition on connect when tracing is active (#5259)

[bobh66]

Acquire the connection before running traces, to prevent race condition.

This change will ensure that the limit and limit_per_host functionality in BaseConnector works when traces are configured.

NOTE: Unit tests are TBD as this is an async race condition which is extremely difficult to unit test. Suggestions are welcome.

Related issue number

Fixes #5259

Checklist

• [X ] I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
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[codecov]

Codecov Report

Merging #5285 (4b695ab) into master (6f73339) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5285      +/-   ##
==========================================
- Coverage   97.54%   97.53%   -0.02%     
==========================================
  Files          43       43              
  Lines        8794     8789       -5     
  Branches     1415     1410       -5     
==========================================
- Hits         8578     8572       -6     
- Misses        101      103       +2     
+ Partials      115      114       -1     

Flag	Coverage Δ
unit	97.41% <100.00%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
aiohttp/connector.py	96.51% <100.00%> (-0.30%)	⬇️
aiohttp/client_exceptions.py	98.33% <0.00%> (-1.67%)	⬇️
aiohttp/cookiejar.py	98.78% <0.00%> (-0.39%)	⬇️
aiohttp/web_server.py	94.28% <0.00%> (-0.16%)	⬇️
aiohttp/pytest_plugin.py	97.45% <0.00%> (-0.05%)	⬇️
aiohttp/web_runner.py	97.76% <0.00%> (-0.01%)	⬇️
aiohttp/web.py	99.14% <0.00%> (-0.01%)	⬇️
aiohttp/abc.py	100.00% <0.00%> (ø)
aiohttp/resolver.py	93.18% <0.00%> (ø)
... and 5 more

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[asvetlov]

Thanks!

[aio-libs-github-bot]

💚 Backport successful

The PR was backported to the following branches:

• ✅ 3.8