ServiceAccount policy is lost when name or description changes

[fgmpe]

Description

When name or description is changed in existing minio_iam_service_account with custom policy, this policy resets to default policy ingerited from minio_iam_user

Steps to Reproduce

1. use aminueza/minio 3.2.0
2. create user and sa

    resource "minio_iam_user" "user" {
      name = "user"
    }
    resource "minio_iam_service_account" "sa" {
      target_user = minio_iam_user.user.id
      name = "name"
      policy = <<-EOT
        {
          "Version": "2012-10-17",
          "Statement": [
            {
              "Effect": "Allow",
              "Action": [ "s3:*" ],
              "Resource": [ "arn:aws:s3:::some-bucket"]
            }
          ]
        }
      EOT
    }
   

3. update name in minio_iam_service_account, apply

Expected behavior: Go to Web UI, go to sa service account of user user and check it's policy - you should see custom policy set above.

Actual behavior: Policy of sa service account is empty.