Fix set ACL fails to existing bucket

ACL API should be called against to an existing bucket.
However current swift3 returns 409 Bucket Already Exists
when the target bucket has already existed.

We should make it to return 200 OK when we can put the ACL
successfully.

Change-Id: I1de6379cbe1fd3eeb7bbcb52a3cf72c5821dfede
Merge "Fix set ACL fails to existing bucket"