Tests update: gameservers_test

[akremsa]

What type of PR is this?

/kind bug
/kind cleanup

What this PR does / Why we need it:
Added missing test cases, abort tests in proper places using require package.

[agones-bot]

Build Succeeded 👏

Build Id: bd947fa3-7243-464d-a268-3ff17776f025

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

• image: gcr.io/agones-images/agones-controller:1.8.0-4c71afe
• image: gcr.io/agones-images/agones-sdk:1.8.0-4c71afe
• image: gcr.io/agones-images/agones-ping:1.8.0-4c71afe
• Linux C++ SDK (build): agonessdk-1.8.0-4c71afe-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.8.0-4c71afe.zip

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

• https://4c71afe-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/1718/head:pr_1718 && git checkout pr_1718
• helm install ./install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.8.0-4c71afe

[google-oss-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: akremsa, roberthbailey

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• OWNERS [roberthbailey]

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