Log Message:
py-minio: updated to 7.1.15

7.1.15
upload_snowball_object(): seek stream to 0 before upload
Revert "list_objecst: fix parsing user metadata as per MinIO server"
Disable multipart upload for upload_snowball_objects() api.
Remove locale usage for datetime parsing
fix policy as a string in presigned_post_policy() API
Add cert_check flag to main class constructor