Fix race condition in SDK.SetLabel and SDK.SetAnnotation (issue #455)

[Yingxin-Jiang]

Fix #455.

When synchronizing GameServer with requested operations, i.e. updateState, updateLabel, updateAnnotation, change the key format from {operation}/{data} to {operation}. The operation data is persisted in SDKServer, to prevent old operation data from overwriting the new one,

[agones-bot]

Build Failed 😱

Build Id: bf0e6e9b-3069-4e30-9c92-ccc1627e182f

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[agones-bot]

Build Failed 😱

Build Id: 68aa9232-93f4-4cd2-bc83-57b409deb59d

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[markmandel]

Meta comment: In the future, can we please get PR titles that are descriptive - it's much faster to parse and then prioritise that way.

[Yingxin-Jiang]

Meta comment: In the future, can we please get PR titles that are descriptive - it's much faster to parse and then prioritise that way.

Sure, good point. I updated this PR title and will use descriptive ones in the future.

The PR was originally sent out with the default title, which I should have paid attention to.

[jkowalski]

can you squish your commits into one, please?

[Yingxin-Jiang]

can you squish your commits into one, please?

Yes, will do. Learning how to :)

[markmandel]

Nice approach! 💯

[Yingxin-Jiang]

Created another PR, #588. Close this one.