Restore connection on network errors

[evgenymarkov]

Problem

If the application is isolated from the Internet, and then access to the Internet is returned, it will no longer recover due to the fact that it will use broken connections.

What do these changes do?

Broken connections in which the StreamReader has an exception (e.g. OSError No route to host) are removed from the connection pool and are no longer reused.

Are there changes in behavior for the user?

Broken connections will be removed from connection pools.

[evgenymarkov]

I created issue #1314

[codecov]

Codecov Report

Merging #1313 (70f9d06) into master (19be499) will decrease coverage by 0.01%.
The diff coverage is 95.12%.

@@            Coverage Diff             @@
##           master    #1313      +/-   ##
==========================================
- Coverage   90.75%   90.74%   -0.02%     
==========================================
  Files          21       21              
  Lines        6947     6988      +41     
  Branches      889      894       +5     
==========================================
+ Hits         6305     6341      +36     
- Misses        469      471       +2     
- Partials      173      176       +3     

Flag	Coverage Δ
unit	90.65% <95.12%> (-0.04%)	⬇️

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Impacted Files	Coverage Δ
aioredis/connection.py	77.32% <85.71%> (+0.02%)	⬆️
tests/test_connection_pool.py	99.41% <100.00%> (+0.03%)	⬆️
aioredis/client.py	82.41% <0.00%> (-0.11%)	⬇️

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