Fix all issues from shellcheck --severity=warning

[johnbley]

Description

Run shellcheck --severity=warning and fix all issues - some from main repo, a dead variable, a safety check to make sure rm -rf doesn't erase the file system, etc.

If desired, I could add a PR for enabling a shellcheck CI step similar to open-telemetry/opentelemetry-lambda#396

Does This PR Require a Core Repo Change?

Some scripts from the core repo also changed, linking both directions for completeness:

• Yes. - Link to PR: Fix shellcheck --severity=warning issues opentelemetry-python#3789
• No.

[lzchen]

Test is failing from an unrelated change. Wait unitl this is merged.

[lzchen]

@johnbley

If desired, I could add a PR for enabling a shellcheck CI step similar to open-telemetry/opentelemetry-lambda#396

I think this would be a great thing to have. Feel free to include that as part of this pr.

[johnbley]

I think [shellcheck CI step] would be a great thing to have. Feel free to include that as part of this pr.

👍