Fix for Unhandled exception related to self.host with unix socket

[winmorre]

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Description of change

Added a fix for Issue #2496 .
Included a try/except block to catch this error and set a default "connection" for the instance when host is not provided

[codecov-commenter]

Codecov Report

Base: 92.22% // Head: 92.22% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (b40f7a9) compared to base (f06f3db).
Patch coverage: 76.92% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2520   +/-   ##
=======================================
  Coverage   92.22%   92.22%           
=======================================
  Files         113      113           
  Lines       29375    29380    +5     
=======================================
+ Hits        27092    27097    +5     
  Misses       2283     2283           

Impacted Files	Coverage Δ
redis/connection.py	86.60% <76.92%> (+0.08%)	⬆️
tests/test_cluster.py	96.90% <0.00%> (-0.12%)	⬇️
tests/test_asyncio/test_cluster.py	97.60% <0.00%> (+0.12%)	⬆️

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