fix: fail over reconnect in stream execution for connection with transaction

[harshit-gangal]

Description

This PR fixes the issue with transactions in OLAP mode, when a connection error occurs, a new connection was getting assigned. This will lead to incorrect transaction behaviour as the old queries inside that transaction were lost.
The correct behaviour is to throw the error back and not start a new connection for that transaction.

Related Issue(s)

Checklist

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Deployment Notes

[vitess-bot]

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[vitess-bot]

I was unable to backport this Pull Request to the following branches: release-15.0.