in_tail: tests about file rotation and deletion sometimes fail

[tagomoris]

On CI environment, tests of in_tail sometimes fails with incorrect number of events, or wrong event order.

• test_rotate_file_with_write_old[parse](TailInputTest::rotate file)
  • https://travis-ci.org/fluent/fluentd/jobs/193651057
  • https://travis-ci.org/fluent/fluentd/jobs/195131107
• test_missing_file(TailInputTest)
  • https://travis-ci.org/fluent/fluentd/jobs/195731891
• test_multiline_with_multiple_formatsflat
  • https://ci.appveyor.com/project/fluent/fluentd/build/2345/job/mgy36d6xqqlye4bt
• test_emit_with_read_lines_limit
  • https://travis-ci.org/fluent/fluentd/jobs/196492970

This shows in_tail potentially has a bug to handle file rotation.

[fujimotos]

This is a follow up comment for this ticket.

Among the 5 items listed in the issue description, I believe the following 3 items
are already fixed (by #1876)

• https://travis-ci.org/fluent/fluentd/jobs/193651057
• https://travis-ci.org/fluent/fluentd/jobs/195731891
• https://travis-ci.org/fluent/fluentd/jobs/196492970

And the remaining problems (which have not been confirmed resolved yet) are:

1. https://ci.appveyor.com/project/fluent/fluentd/build/2345/job/mgy36d6xqqlye4bt
2. https://travis-ci.org/fluent/fluentd/jobs/195131107

Note that Problem 1 is possibly resolved by now since we do not see failures on
appveyor for a while, and Problem 2 is very likely an OSX-specific issue...

[ashie]

After adding some more changes to in_tail plugin and its tests, recent days we don't see such failures.
So I close this issue.
We should update information about unstable tests.

[ashie]

For windows, I've found a bug in the tests: #3767