This addresses the regression in Hadoop 3.3.1 where if no S3 endpoint
is set in fs.s3a.endpoint, S3A filesystem creation may fail on
non-EC2 deployments, depending on the local host environment setup.
* If fs.s3a.endpoint is empty/null, and fs.s3a.endpoint.region
is null, the region is set to "us-east-1".
* If fs.s3a.endpoint.region is explicitly set to "" then the client
falls back to the SDK region resolution chain; this works on EC2
* Details in troubleshooting.md, including a workaround for Hadoop-3.3.1+
* Also contains some minor restructuring of troubleshooting.md
Contributed by Steve Loughran.
5b7f68ac76