When a bucket already exists, PUT returned a BucketAlreadyExists error.
AWS S3 returns BucketAlreadyOwnedByYou error instead, so this changes
the error returned by swift3.
When sending a PUT request to a bucket, if the bucket already exists and
is not owned by the user, return 409 conflict error,
BucketAlreadyExists.
Change-Id: I32a0a9add57ca0e4d667b5eb538dc6ea53359944
Closes-Bug: #1498231