ceph: fix SignatureDoesNotMatch by using correct secret key (apache#11115)

Ensure bucket.getSecretKey() is used when building the S3 client.
Previously, only getAccessKey() was passed for both key and secret,
causing V4 signature validation failures during operations such as
bucket creation and policy updates.

Co-authored-by: Jean Vetorello <[email protected]>

Author: 2 people