[aws-ints] fixing cloudtrail records parsing

[jvanbrie]

What does this PR do?

There are some cloudtrail logs that don't come with the s3 "Records" field. This pr accounts for that by not assuming the field exists.

Motivation

Issues with this parsing found here: #593

Testing Guidelines

Generated a lambda layer off of this change and it's running fine.

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
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