Support signing global aws requests
Support signing global aws requests

Prior, an endpoint format was being assumed that is not compatible
with public endpoints. Now, us-east-1 will be returned for global
endpoints, as mentioned in aws docs. Support for all default
partitions has been added.

rancher/rancher,rancher/rancher,rancher/rancher,rancherio/rancher,rancherio/rancher,rancher/rancher