Previously, Nomad used hand rolled HTTP requests to interact with the
EC2 metadata API. Recently however, we switched to using the AWS SDK for
this fingerprinting.

The default behaviour of the AWS SDK is to perform retries with
exponential backoff when a request fails. This is problematic for Nomad,
because interacting with the EC2 API is in our client start path.

Here we revert to our pre-existing behaviour of not performing retries
in the fast path, as if the metadata service is unavailable, it's likely
that nomad is not running in AWS.