Close a Connection whenever an exception is raised for send_command()

[kristjanvalur]

The api does not allow for a "resume", e.g. on a timeout, because an unknown number of bytes has been sent and an internal send state is not maintained. Therefore, there is no point in keeping the connection open.

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Description of change

The discussion at #2560 pointed out that there is no way an open Connecition after a failed send_command() call can be useful. This PR therefore closes the Connection on every exception in that case, thus partially reverts a change made in #2104

[codecov-commenter]

Codecov Report

Base: 92.20% // Head: 92.21% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (e80f72e) compared to base (74c251a).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2516   +/-   ##
=======================================
  Coverage   92.20%   92.21%           
=======================================
  Files         113      113           
  Lines       29357    29357           
=======================================
+ Hits        27070    27072    +2     
+ Misses       2287     2285    -2     

Impacted Files	Coverage Δ
redis/asyncio/connection.py	86.57% <0.00%> (ø)
redis/connection.py	86.52% <0.00%> (ø)
tests/test_cluster.py	97.01% <0.00%> (+0.11%)	⬆️

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[kristjanvalur]

Closing this in favour of #2506