FLUME-3320 Fix taildir source reset position bug

[iijima-satoshi]

https://issues.apache.org/jira/browse/FLUME-3320

[rgoers]

There are 12 open PRs against taildir source. Before applying this I really need to know if this causes any of the other PRs to be moot. Or looking at it from the other perspective, if those PRs are applied what impact will they have on this one.

[iijima-satoshi]

#297 is duplicated with this and is not sufficient to prevent this problem.
The reason is the following (my Jira comment).

I've met the same problem recently. This is because inode, filesize and lastModifiedTime are retrieved at different times.
To resolve this completely, it is necessary to retrieve these at the same time. I created a PR for this.

Therefore, if this PR is applied, #297 is unnecessary.

Other 11 PRs are derived from different problems and this PR would not affect the other PRs.

Additionally, I commented some PRs that I can understand.

[rgoers]

Is it possible to create a test that fails without this change and succeeds when it is applied? How can I verify this fixes the problem?