Add curl timeout

[jmorten]

Please ensure the following before submitting a PR:

• if suggesting code changes or improvements, open an issue first
• [n/a] for all but trivial changes (e.g., typo fixes), add your name to DESCRIPTION
• [n/a] for all but trivial changes (e.g., typo fixes), documentation your change in NEWS.md with a parenthetical reference to the issue number being addressed
• [n/a] if changing documentation, edit files in /R not /man and run devtools::document() to update documentation
• [n/a] add code or new test files to /tests for any new functionality or bug fix
• make sure R CMD check runs without error before submitting the PR

[jmorten]

The failed checks don't seem like it was an issue with the code.

[antoine-sachet]

I understand why you did this (I am running into the same slowness issue on my local machine, related to cloudyr/aws.signature#33 and #7) but I am concerned that this may break my production code (actually running on ec2 and ecs). What if AWS takes more than 100ms to respond?

[jon-mago]

Hi!

Thanks so much for this. I'm sorry it's taken me forever to review it.

I'm happy with this change in principle, but I'd like to change the timeout to 1000ms to bring it in line with the default timeout from boto3 (controlled by AWS_METADATA_SERVICE_TIMEOUT).