Automatic merge from submit-queue (batch tested with PRs 60433, 59982, 59128, 60243, 60440). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
[fluentd-gcp addon] Update to use Stackdriver Agent image.
Update the fluentd DaemonSet to use the Stackdriver Logging Agent container image.
The Stackdriver Logging Agent container image uses fluentd v0.14.25.
We add a special label to each log record as a signal to logging backends to handle both new and legacy resource types.
**Release note:**
```release-note
[fluentd-gcp addon] Switch to the image, provided by Stackdriver.
```
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