minio: update documentation in regards to #3478
minio: update documentation in regards to #3478

creating custom access/secret keys without properly base64 encoding them resulted in failed access to minio dashboard

Signed-off-by: jbmcfar <b4a230f48f6f65592d353c376acbcb4091dc8ced@sandia.gov>

rook/rook,rook/nfs,rook/nfs,rook/nfs,rook/rook,rook/rook,rook/rook,rook/rook