async function ensureUnmount (fs, path) {
  try {
    let st = await fs.stat(path).catch(e => null)
    if (st && st.mount) {
      // remove mount
      await fs.unmount(path)
    }
  } catch (e) {
    console.error('Filesystem failed to unmount drive', {path, error: e})
  }
}
@param {Hyperdrive} fs
@param {string} path 
@return {Promise<void>}