This commit replaces the custom KES client implementation
with the KES SDK from https://github.com/minio/kes
The SDK supports multi-server client load-balancing and
requests retry out of the box. Therefore, this change reduces
the overall complexity within the MinIO server and there
is no need to maintain two separate client implementations.
Signed-off-by: Andreas Auernhammer <aead@mail.de>
