Added Integration Tests for download.AmerifluxLBL

[meetagrawal09]

Description

This PR aims to add integration tests for the data item : AmerifluxLBL

Review Time Estimate

• Immediately
• Within one week
• When possible

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• My name is in the list of CITATION.cff
• I have updated the CHANGELOG.md.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[mdietze]

While this PR and the other met download PRs do represent useful tests of whether the underlying APIs we use are responding, they aren't actually integration tests. I'm not even sure they count as unit tests since they're not actually testing the download functions that we're currently using. (aside: I wonder if it'd be possible, once files are downloaded in the current piecemeal fashion, to use them in mocking the responses to the overall function unit tests). More importantly, they current unit tests are definitely not integration testing the larger met.process workflow. As such, I worry that we may be missing opportunities to identify the larger issues in that workflow and are investing time in fixing things that may not be the parts that are actually broken.