Consistently use enum raw value instead of description on the command line

[rgoldberg]

Consistently use enum raw value instead of description on the command line. See issue #771.

Checklist

• I've added at least one test that validates that my change is working, if appropriate
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary

[natecook1000]

@swift-ci Please test

[rauhul]

@swift-ci test