[GROW-3134] release already acquired connections, when get_connections raised an exception

[zach-iee]

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Description of change

when writing test for a custom patch that we've made, i found out that we may be leaking connections in the below scenario

scenario:
1. pipeline needs to be executed on multiple nodes (node 1 and node2)
2. obtain a connection for node 1
3. failed to obtain a connection for node 2 due to ConnectionError or TimeoutError
4. repeat 2 and 3 until it succeeds

In the above scenario, the connection on node 1 that we've acquired doesn't get released forever as we lose reference to the connection, when an exception is raised

FYI there may be more connection leaks, but we need to monitor after this gets applied

Please provide a description of the change here.

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.21 🎉

Comparison is base (8a7897c) 92.10% compared to head (433e481) 92.32%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master       #3      +/-   ##
==========================================
+ Coverage   92.10%   92.32%   +0.21%     
==========================================
  Files         119      119              
  Lines       30547    30567      +20     
==========================================
+ Hits        28136    28221      +85     
+ Misses       2411     2346      -65     

Impacted Files	Coverage Δ
redis/cluster.py	90.58% <100.00%> (+1.05%)	⬆️
tests/test_cluster.py	96.77% <100.00%> (+0.13%)	⬆️

... and 14 files with indirect coverage changes

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