Grafana - add namespace to autoscalers dashboard

[akremsa]

What type of PR is this?**

/kind bug

What this PR does / Why we need it:
Now we can filter autoscalers dashboards data by namespace.

Which issue(s) this PR fixes:
Closes #1501

Special notes for your reviewer:

[aLekSer]

It looks fine to me.

[google-oss-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: akremsa, aLekSer
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[google-oss-robot]

New changes are detected. LGTM label has been removed.

[agones-bot]

Build Succeeded 👏

Build Id: 7f0f06e5-dd11-4870-8391-f120eb085458

The following development artifacts have been built, and will exist for the next 30 days:

• image: gcr.io/agones-images/agones-controller:1.7.0-a6dccd5
• image: gcr.io/agones-images/agones-sdk:1.7.0-a6dccd5
• image: gcr.io/agones-images/agones-ping:1.7.0-a6dccd5
• Linux C++ SDK (build): agonessdk-1.7.0-a6dccd5-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.7.0-a6dccd5.zip

A preview of the website (the last 30 builds are retained):

• https://a6dccd5-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/GoogleCloudPlatform/agones.git pull/1615/head:pr_1615 && git checkout pr_1615
• helm install ./install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.7.0-a6dccd5