Prevent race conditions by syncing node cache on GameServer controller

[markmandel]

Added cache.InformerSynced for Nodes on startup, to avoid race conditions.

This also included fix for flakey tests for the same reason.

[agones-bot]

Build Failed 😱

Build Id: ca16976a-0990-4e26-b2be-4e47b4de7e28

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[agones-bot]

Build Succeeded 👏

Build Id: 7b59e4d0-766e-4463-8035-8cc9b1be68b1

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

• image: gcr.io/agones-images/agones-controller:0.10.0-e029a9e
• image: gcr.io/agones-images/agones-sdk:0.10.0-e029a9e
• image: gcr.io/agones-images/agones-ping:0.10.0-e029a9e
• Linux C++ SDK (build): agonessdk-0.10.0-e029a9e-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-0.10.0-e029a9e.zip

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

• https://e029a9e-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/GoogleCloudPlatform/agones.git pull/782/head:pr_782 && git checkout pr_782
• helm install install/helm/agones --namespace agones-system --name agones --set agones.image.tag=0.10.0-e029a9e