Bump versions of components with latest security patches.

[loburm]

What this PR does / why we need it:
Upgrade versions of monitoring components used on GCP, to include latest security patches.

Release note:

[fluentd-gcp-scaler addon] Bump fluentd-gcp-scaler to 0.4 to pick up security fixes.
[prometheus-to-sd addon] Bump prometheus-to-sd to 0.3.1 to pick up security fixes, bug fixes and new features.
[event-exporter addon] Bump event-exporter to 0.2.3 to pick up security fixes.

[loburm]

/assign @timstclair

[loburm]

/test pull-kubernetes-e2e-kops-aws

[loburm]

/test pull-kubernetes-e2e-kops-aws

[tallclair]

/lgtm

[loburm]

/assign @cjcullen @piosz

[loburm]

/retest

[piosz]

/lgtm
/approve

[loburm]

/assign @mikedanese

[loburm]

/assign @Q-Lee

[loburm]

/test pull-kubernetes-e2e-gke

[tallclair]

/milestone v1.12

[mikedanese]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: loburm, mikedanese, piosz, tallclair

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Needs approval from an approver in each of these files:

• cluster/addons/cluster-monitoring/OWNERS [mikedanese,piosz]
• cluster/addons/fluentd-gcp/OWNERS [mikedanese,piosz]
• cluster/addons/metadata-proxy/OWNERS [mikedanese]
• test/e2e/instrumentation/OWNERS [mikedanese,piosz]

Approvers can indicate their approval by writing /approve in a comment
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[fejta-bot]

/retest
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[loburm]

/test pull-kubernetes-e2e-gke

[loburm]

/test pull-kubernetes-e2e-gke

[fejta-bot]

/retest
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Review the full test history for this PR.

Silence the bot with an /lgtm cancel comment for consistent failures.

[fejta-bot]

/retest
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Review the full test history for this PR.

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[mikedanese]

This is a critical security fix.

[k8s-github-robot]

/test all [submit-queue is verifying that this PR is safe to merge]

[k8s-ci-robot]

@loburm: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
pull-kubernetes-integration	ffa934a	link	/test pull-kubernetes-integration

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[k8s-github-robot]

Automatic merge from submit-queue (batch tested with PRs 67691, 68147). If you want to cherry-pick this change to another branch, please follow the instructions here: https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md.