fix: preserve AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE env variable

[LennartKoot]

Proposed changes

Fixes #410

Preserves the AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE environment variable for worker threads so the gateway can properly use the associated pod identity instead of using the node's identity.

On our cluster we restricted using the node's identity, so this resulted in an error when retrieving the AWS credentials:

2025/09/08 13:13:12 [info] 78#78: *2 js: Cached credentials are expired or not present, requesting new ones
2025/09/08 13:14:12 [info] 78#78: *2 js: Could not load EC2 task role credentials: {}

With this environment variable preserved, the 'Could not load' error is not happening anymore.

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[github-actions]

✅ All required contributors have signed the F5 CLA for this PR. Thank you!
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[LennartKoot]

I have hereby read the F5 CLA and agree to its terms

[dekobon]

Looks good to me. Thank you for your contribution.