DDC-4022: [GH-1574] deduplication of internal UnitOfWork methods

[doctrinebot]

Jira issue originally created by user @doctrinebot:

This issue is created automatically through a Github pull request on behalf of Ma27:

Url: #1574

Message:

the methods UnitOfWork#afterTransactionRolledBack() and UnitOfWork#afterTransactionComplete do almost the same, so it can be abstracted into another private method.

[nowiko]

Hello, @beberlei , it seems like this issue can be closed, regarding this commit.

[Ocramius]

Linking #5549 and #1574

Thanks @NovikovViktor!