test_sts: Changing code for proper cleanup
test_sts: Changing code for proper cleanup

This solves: https://tracker.ceph.com/issues/53090

The solution is: We need to delete the role_policy and
user_policy attached user which was causing the failure.

Signed-off-by: Kalpesh Pandya <a64d0445eb0581c9d2267611630ddf78466bef3d@redhat.com>

ceph/s3-tests,ceph/s3-tests