[fix] trigger reconcile if driver pod Waiting

[aagumin]

Purpose of this PR

Fixing a bug where the SparkApplication did not transition to Failed when the driver pod, while in pending status, received an ErrImagePull.

Proposed changes:

• Extend pkg/util/sparkpod_test.go
• Exercise controller-specific logic such as ShouldProcessPodUpdate, driver failure reason detection, and unschedulable transitions.
• Add reusable pod/status builders to keep complex test scenarios concise.

Change Category

• Bugfix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that could affect existing functionality)
• Documentation update

Rationale

These helpers are central to the controller’s reconciliation flow. Covering them with table-top tests protects against regressions when adjusting pod labels, conditions, or driver-specific status handling.

Checklist

• I have conducted a self-review of my own code.
• I have updated documentation accordingly.
• I have added tests that prove my changes are effective or that my feature works.
• Existing unit tests pass locally with my changes.

Additional Notes

I’m not sure the solution is correct, but the bug is fixed.

[google-oss-prow]

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[aagumin]

/cc @ChenYi015 Hi! Review pls my PR