Apps that are explicitly not to be platform_managed are being picked

[Thiago Paiva Brito]

Brief Description
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Apps that explicitly define platform_managed_app as 'no', 'false' or '0' are being picked up to be platform managed nonetheless.

Probably a misuse of common.utils.is_valid_boolstr at https://github.com/starlingx/config/blob/master/sysinv/sysinv/sysinv/sysinv/conductor/kube_app.py#L2583

Severity
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Minor: System/Feature is usable with minor issue

Steps to Reproduce
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Write down the steps to reproduce the issue

Expected Behavior
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App is not picked up to be platform managed on sysinv's periodic task

Actual Behavior
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App is picked up to be platform managed on sysinv's periodic check

Reproducibility
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5/5

Test Activity
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Developer Testing

Workaround
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remove platform_managed_app from metadata.yaml