fix(container): fix a bug in GKE blue green upgrade policy

[zicongmei]

This is fixing the issue reported in hashicorp/terraform-provider-google#25757.
Fixes hashicorp/terraform-provider-google#25757

The validation code previously take an empty list as a configured value. And therefore incorrectly think the standard_rollout_policy and autoscaled_rollout_policy.

Verification:

1. Created a tf file to reproduce the problem.
2. Change the code and built a provider locally.
3. Verify the new provider doesn't have this bug anymore.

Release Note Template for Downstream PRs (will be copied)

See Write release notes for guidance.

container: fixed a bug in `google_container_node_pool` that prevented creation when `blue_green_settings` was specified

[github-actions]

Hello! I am a robot. Tests will require approval from a repository maintainer to run.

Googlers: For automatic test runs see go/terraform-auto-test-runs.

@roaks3, a repository maintainer, has been assigned to review your changes. If you have not received review feedback within 2 business days, please leave a comment on this PR asking them to take a look.

You can help make sure that review is quick by doing a self-review and by running impacted tests locally.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google-beta provider: Diff ( 1 file changed, 2 insertions(+), 2 deletions(-))

[modular-magician]

Tests analytics

Total tests: 279
Passed tests: 264
Skipped tests: 15
Affected tests: 0

Click here to see the affected service packages

• container

🟢 All tests passed!

View the build log