Support for AWS Route53 in China

[greenu]

Recently AWS Route53 was introduced to AWS China region.
This PR updates aws-go-sdk to fix Route53 endpoints for China and fixes invalid ELB hostedzones for cn-north-1 and cn-northwest-1
https://docs.aws.amazon.com/general/latest/gr/elb.html for reference.

Fixes #1486 and probably #1544

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[greenu]

/assign @Raffo

[njuettner]

/lgtm

[Raffo]

/approve

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