S3: Allow bucket creation besides us-east-1 for AWS

[mdedetrich]

There seems to be another inconsistency between real AWS and Minio wrt creating a bucket in the non default region (i.e. us-east-1). With AWS S3 you need an addition XML payload (along with the host/access-style which typically contains the region) in order to create a bucket in a non default us-east-1 region, with Minio this payload is not required. If the XML payload is not in the make bucket request on AWS you will get the following error

The unspecified location constraint is incompatible for the region specific endpoint this request was sent to..

For more details you can read https://docs.aws.amazon.com/AmazonS3/latest/API/API_CreateBucket.html , there is already an existing issue at aws/aws-cli#2603 (comment) which demonstrates the same problem (i.e. even with the aws cli you need to provide an additional LocationConstraint).

A test is provided but do note the fixes on this PR are only verifiable when running the test against AWSS3IntegrationSpec. With MinioS3IntegrationSpec you won't notice any difference.

[ennru]

LGTM.

[ennru]

Thank you for all the great additions and fixes!