fix: Fixed potential deadlock from unexpected __del__ call

[vladvildanov]

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Description of change

Fixes potential deadlock when GC takes action and __del__ invoked in the middle of get_connection() or release() methods. ClusterPipeline object releases connection on __del__ method which leads to a deadlock.

This PR introduces only non-breaking changing fixes, the follow up PR with backward incompatible fixes will be released as a part of next major release

Closes #3289

[petyaslavova]

LGTM.