Updates to objects in S3 are only eventually consistent. If the
RemoteClient has a DynamoDB table available, use that to store a
checksum of the last written state, so the object can be verified by the
next client to call Get.
Terraform currently doesn't have any sort of user feedback around
RefreshState/Get, so we poll only for a short time before returning an
error.
Move the S3 State from a legacy remote state to an official backend.
This increases test coverage, uses a set schema for configuration, and
will allow new backend features to be implemented for the S3 state, e.g.
"environments".
James Bardin