rgw: fix the condition of authenticated user's permit check

rgw: fix the condition of authenticated user's permit check

before fix:
put a bucket under one user with authenticated-read permit
> ./s3curl.pl http://myobs.com/mybucket --put --H "x-amz-acl: authenticated-read"
GET the bucket with anonymous user
> curl http://myobs.com/mybucket -X GET

> successed!

after fix:
anonymous cant GET the authenticated-read bucket
other users who authenticated could GET it

Signed-off-by: Zengran Zhang <zhangzengran@h3c.com>