Fix/s3 errors

[raclim]

Progress on #3096

Changes:

• Updates error handling for server/controllers/aws.controller.js
• Converts the remaining methods in server/models/user.js to async/await syntax

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

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