Fix fips-us-gov-west-1 s3 logic

The s3.json model had "fips-gov-west-1" when the
region needed to be "fips-us-gov-west-1".  Interestingly
enough, botocore did *not* given an error when this happened.
This should be fixed...
Add test for endpoint global logic

This didn't make sense to me at first, but for a number of reasons
(noted in the comments) we can't change this behavior just yet.
Otherwise this would be a breaking change to the CLI.  I think there's
probably a better way to do this, but for now leaving things as is.  I
did add a test that documents this behavior though, so hopefully
others don't hit this code and wonder what's going on.
Merge branch 'fix-s3-fips-endpoint' into develop

* fix-s3-fips-endpoint:
  Add test for endpoint global logic
  Fix fips-us-gov-west-1 s3 logic