Handle no creds in service-account-credentials

[delgadom]

Right now if there are no credential files in ~/service-account-credentials, a single directory, '*', is created in /gcs. The behavior should be to take no action.

Workflow

• [ ] Closes issue #
• [ ] Notebook:worker pairing builds & passes local build, visual inspection & client.map tests
• [ ] Passes travis tests
• [ ] Image deployed on dev branch (see notebook and worker dev tags)
• [ ] Worker passes manual deployment test on compute.rhg
• [ ] Notebook+worker passes test-hub deployment
• [ ] Updates integrated into downstream images

Summary

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Features

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