Update tail to use polling instead of fsnotify

fsnotify is difficult to use correctly, especially in the face of usage
of symlinks like we often see in kube. The stat() calls will only happen
while waiting for additional data and not on a continual basis.

collector/logs/sources/tail/tail.go

@@ -199,7 +199,7 @@ func (s *TailSource) AddTarget(target FileTailTarget, updateChan <-chan FileTail
 	tailerCtx, shutdown := context.WithCancel(s.groupCtx)
 	batchQueue := make(chan *types.Log, 512)
 	outputQueue := make(chan *types.LogBatch, 1)
-	tailConfig := tail.Config{Follow: true, ReOpen: true}
+	tailConfig := tail.Config{Follow: true, ReOpen: true, Poll: true}
 	existingCursorPath := cursorPath(s.cursorDirectory, target.FilePath)
 	fileId, position, err := readCursor(existingCursorPath)
 	if err == nil {