Fix GKE autoscaling conditions in reconciliation process

[kahun]

What type of PR is this?
/kind bug

What this PR does / why we need it:
The reconciliation process is broken in GKE. When enableAutoscaling is not defined, the reconciliation process fails because desiredAutoscaling is nil and when it is defined, it fails because the state is unexported.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Fix GKE autoscaling conditions in reconciliation process.

[k8s-ci-robot]

Hi @kahun. Thanks for your PR.

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[cpanato]

/ok-to-test

[cpanato]

/approve

/assign @richardcase

thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cpanato, kahun

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[richardcase]

Thanks @kahun

/lgtm