Ensure tombstones created before kubexit started are read

[RemcodM]

fixes #8

This commit changes the Watch function inside the tombstone package to also emit an initial event besides the fsnotify events. This initial event is called immediatly when Watch is called and the watcher has been setup.

This change allows kubexit to detect tombstones written before kubexit was started. This prevents possible race conditions as described by #8.

In order for this change to work, the tombstone.EventHandler type was changed. It now requires a function with 3 arguments: The graveyard, the tombstone and the operation instead of an fsnotify.Event. Reason being that the initial event is not an fsnotify.Event. The functions implementing a tombstone.EventHandler are changed accordingly.

This change on its own introduces a new bug where the tombstone is written as part of an initial event, but the child process will still start because child.Start() is being called after the watcher has been setup. To overcome this issue, the shutdown state of the child is tracked in a new flag, which is set if ShutdownNow() or ShutdownWithTimeout() is executed.

[karlkfi]

Thanks for the bug report, but I think this refactor is probably unnecessary. It's probably cleaner to just trigger the event handler with a fake create event, since the struct, type, and constants are public. https://github.com/fsnotify/fsnotify/blob/master/fsnotify.go#L16-L32

files, err := ioutil.ReadDir(graveyard)
if err != nil {
	return fmt.Errorf("failed to read graveyard dir: %v", err)
}

for _, f := range files {
	event := fsnotify.Event{
		Name:	filepath.Join(graveyard, f.Name())
		Op:		fsnotify.Create,
	}
	eventHandler(event)
}

[RemcodM]

Superseded by #10