Inaccurate error message when failing to upload fluxcd applications

Brief Description
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When running 'system application-upload <APPLICATION>.tgz' with a fluxcd application, on failure, the message is inaccurate. This can occur when the tgz files has a missing kustomization.yaml file. The error reported by the system is "Application-upload rejected: Application-upload rejected: manifest file/directory is missing.", however no manifest file is needed in a fluxcd application.

Severity
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Minor: System/Feature is usable with minor issue

Steps to Reproduce
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- Create a fluxcd with a missing kustomization.yaml
- Run 'system application-upload <APPLICATION>.tgz' and note the inaccurate error

Expected Behavior
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Error message should indicate the kustomization.yaml is missing not the manifest.

Actual Behavior
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The error message returned is "Application-upload rejected: Application-upload rejected: manifest file/directory is missing."

Reproducibility
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100%

System Configuration
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Testing on AIO-SX

Branch/Pull Time/Commit
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Master

Last Pass
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New feature

Timestamp/Logs
--------------

Test Activity
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Developer testing

Workaround
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A properly packaged fluxcd application.