Fixes a race where the log reader would get events for both an actual
rotation as we from fsnotify (`fsnotify.Rename`).
This issue becomes extremely apparent when rotations are fast, for
example:
```
$ docker run -d --name test --log-opt max-size=1 --log-opt max-file=2
busybox sh -c 'while true; do echo hello; usleep 100000; done'
```
With this change the log reader for jsonlogs can handle rotations that
happen as above.
Instead of listening for both fs events AND rotation events
simultaneously, potentially meaning we see 2 rotations for only a single
rotation due to channel buffering, only listen for fs events (like
`Rename`) and then wait to be notified about rotation by the logger.
This makes sure that we don't see 2 rotations for 1, and that we don't
start trying to read until the logger is actually ready for us to.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
84e60a7e10