Fixes log reopening.

[vladlosev]

This fixes a situation when logs are rotated via movement.

1. A log is rotated.
2. The library sees that, closes the watch on the file, and sets up a directory watch for the file to appear.
3. New log file is created.
4. The library sees the file created, and removes the directory watch
5. The library creates a watch on the file itself now that the file is present.

In the current code, (4) cleans up the done channel but then removes the directory watch and exits without instructing the InotifyTracker::run to complete the cleanup via the removeWatch method. This results in the event channel for the file not being cleaned up. It's not a problem in itself, but then in (5), addWatch uses the presence of the event channel to decide whether initialize both events and done channel. As the event channel is still present, the done channel is not initialized. Subsequently, absence of the done channel prevents sendEvents from forwarding fsnotify events to clients.

This change makes a separate check for presence of the of the done channel in order to initialize it. The changes in the test introduce stricter checks: without them the test hangs and is subsequently terminated as lines are not being delivered to the reader.

[vladlosev]

@negator would like your 👀 on this. Please also loop in anyone else who can contribute a good review. Once this looks good, I will send another PR against upstream.

[negator]

lgtm