Summary:
There are some old fashioned tests that use ysqlsh executable instead of libpq.
It could happen that postgres was not yet started when test is trying to connect to it.
Out libpq wrapper already has retry mechanism for this scenario.
Added similar logic to RunPsqlCommand so test would not fail because postgres is not yet ready.
Jira: DB-6409

Test Plan: ./yb_build.sh release -n 40 --cxx-test tools_yb-backup-cross-feature-test --gtest_filter YBBackupTest.TestYSQLPartitioningVersion

Reviewers: hsunder

Reviewed By: hsunder

Subscribers: yql, ybase

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D41457