JIRA: https://jira.spring.io/browse/INT-3464
Previously, if an IO exeption occurred while synchronizing
files, and an AcceptOnceFileListFilter is being used, files that were
not transferred would not be fetched next time.
Add strategy `ReversibleFileListFilter` that can rollback previously
accepted files.
Implement this interface on `AcceptOnceFileListFilter` and
`AbstractPersistentAcceptOnceFileListFilter`.
Add test cases.
Polishing
a20fa9a029