Control container doesn't support bringing my own `ca-bundle.crt`

**Image I'm using:**
Latest

**Issue:**
The [certificate logic](https://github.com/bottlerocket-os/bottlerocket-control-container/blob/4e04695e7f4bb5ad05e9ea54b7f69c0ec4249487/start_control_ssm.sh#L18) used by control container doesn't account for a file that already exists with the same name.

This results in the following error:

```
host-containers@control[1394]: ln: failed to create symbolic link '/etc/pki/ca-trust/source/anchors/ca-bundle.crt': File exists
host-containers@control[1394]: time="2025-03-26T10:00:01Z" level=fatal msg="Container control exited with non-zero status"
```