Get the gs state correctly in error message

[gongmax]

What type of PR is this?

Uncomment only one /kind <> line, press enter to put that in a new line, and remove leading whitespace from that line:

/kind breaking

/kind bug

/kind cleanup
/kind documentation
/kind feature
/kind hotfix
/kind release

What this PR does / Why we need it:
When Update fails, the returned gs is nil. Change to get the GameServer state properly from gsCopy.

Which issue(s) this PR fixes:

Closes #

Special notes for your reviewer:

[agones-bot]

Build Failed 😱

Build Id: 8da97454-db5f-44b1-b9ab-cbc57cb0ef45

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[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gongmax, markmandel

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[markmandel]

Possible new flake:

Trace[539986959]: [29.993551965s] [29.993551965s] END
panic: test timed out after 10m0s
running tests:
	TestControllerSyncGameServer (9m59s)
	TestControllerSyncGameServer/Creating_a_new_GameServer (9m59s)

[agones-bot]

Build Succeeded 👏

Build Id: 2bd92212-cfce-4f1f-b678-192486f8c96f

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

• image: us-docker.pkg.dev/agones-images/ci/agones-controller:1.35.0-dev-2c7c24f-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.35.0-dev-2c7c24f-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.35.0-dev-2c7c24f-linux-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.35.0-dev-2c7c24f-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.35.0-dev-2c7c24f-amd64
• Linux C++ SDK (build): agonessdk-1.35.0-dev-2c7c24f-amd64-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.35.0-dev-2c7c24f-amd64.zip

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

• https://2c7c24f-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/3385/head:pr_3385 && git checkout pr_3385
• helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.35.0-dev-2c7c24f-amd64