ecs-init: Add ISO partition for downloading agent appropriately

[singholt]

Summary

This PR adds the ISO partition ID and the region to the partitionBucketRegion mapping. ECS init goes looking for where to download ecs agent from, but fails for ISO regions. With this change, it should now be able to look in the right place.

Implementation details

We use the identifier defined in aws-sdk:

amazon-ecs-agent/ecs-init/vendor/github.com/aws/aws-sdk-go/aws/endpoints/defaults.go

Lines 10 to 16 in 7060c3f

	const (
	AwsPartitionID = "aws" // AWS Standard partition.
	AwsCnPartitionID = "aws-cn" // AWS China partition.
	AwsUsGovPartitionID = "aws-us-gov" // AWS GovCloud (US) partition.
	AwsIsoPartitionID = "aws-iso" // AWS ISO (US) partition.
	AwsIsoBPartitionID = "aws-iso-b" // AWS ISOB (US) partition.
	)

Testing

New tests cover the changes: no

Description for the changelog

Fix: Add ISO partition for downloading agent appropriately

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[Realmonia]

What's the use case of this change? (specifically when does this happen?)

ECS init goes looking for where to download ecs agent from, but fails for ISO regions.

Nvm I see the thread on slack. Can we also make sure the S3 url in ISO is the same as that of commercial regions?

[singholt]

What's the use case of this change? (specifically when does this happen?)

ECS init goes looking for where to download ecs agent from, but fails for ISO regions.

Nvm I see the thread on slack. Can we also make sure the S3 url in ISO is the same as that of commercial regions?

yes I'll work with the engineer assisting us to test this and verify before merging.

[YashdalfTheGray]

These exist in the SDK, so we're good to go here.

[singholt]

What's the use case of this change? (specifically when does this happen?)

ECS init goes looking for where to download ecs agent from, but fails for ISO regions.

Nvm I see the thread on slack. Can we also make sure the S3 url in ISO is the same as that of commercial regions?

yes I'll work with the engineer assisting us to test this and verify before merging.

verified this fixes the error (logged as a warning in ecs init logs). Merging.