Add support for us-gov-west-1 region

Author: Dan Isla

src/main/java/org/elasticsearch/cloud/aws/InternalAwsS3Service.java

@@ -169,7 +169,9 @@ private static String getEndpoint(String region) {
  return "s3-us-west-1.amazonaws.com";
  } else if ("us-west-2".equals(region)) {
  return "s3-us-west-2.amazonaws.com";
- } else if ("ap-southeast".equals(region)) {
+ } else if ("us-gov-west-1".equals(region)) {
+ return "s3-us-gov-west-1.amazonaws.com";
+ }else if ("ap-southeast".equals(region)) {
  return "s3-ap-southeast-1.amazonaws.com";
  } else if ("ap-southeast-1".equals(region)) {
  return "s3-ap-southeast-1.amazonaws.com";