Integration tests occasionally fail with 404 errors

[ljfranklin]

Seems to be some eventual consistency issue with S3:

Expected S3 file 'terraform-test-unit/out-test-72657703.tfstate.tainted' to exist in bucket 'terraform-resource-ci', but it does not
  Expected error:
      <*awserr.requestError | 0xc42046b050>: {
          awsError: {code: "NotFound", message: "Not Found", errs: nil},
          statusCode: 404,
          requestID: "E4F9EC73626A515C",
      }
      NotFound: Not Found
      	status code: 404, request id: E4F9EC73626A515C
  not to have occurred

One failed build is here

[ljfranklin]

This should be fixed here: 9bd272e