Add restart UnitOfWork by a single operation

[zubaidullo]

Add restart UnitOfWork by a single operation.
This will allow users to restart UnitOfWork by a single operation.

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[sameb]

Hello, unfortunately I cannot accept this PR as the CLA is not signed. If you'd like to resubmit a new PR, please do so, sign the CLA, and also clearly explain why the restart() method is necessary.

It's also possible that the reason for this PR was obsoleted by 3e21a13.