ModifyBucketPolicy merged the caller's statement into the policy fetched
from the bucket, matching by SID. Besides a missing match flag that
appended a duplicate when a SID matched, this preserved any pre-existing
statements on the bucket and reapplied them on every reconcile.
Overwrite the policy with the provided statements instead, so a managed
bucket always ends up with exactly the intended policy and cannot retain
unexpected statements.
Signed-off-by: Artem Muterko <artem@sopho.tech>
(cherry picked from commit 321911b96c)