message: fix(nydus-snapshotter): fix p.Wait() return err when destroy nydusd
  When nydus-snapshotter restart, it will break the relationship between nydusd and
  nydus-snapshotter, so p.Wait() will return err. This pr fix the err by
  judge the err type
diff: @@ -8,6 +8,7 @@ package process
  import (
  "context"
  + stderrors "errors"
  "fmt"
  "os"
  "os/exec"
  @@ -194,8 +195,10 @@ func (m *Manager) DestroyDaemon(d *daemon.Daemon) error {
  return err
  }
  _, err = p.Wait()
  - if err != nil {
  - return err
  + // if nydus-snapshotter restart, it will break the relationship between nydusd and
  + // nydus-snapshotter, p.Wait() will return err, so here should exclude this case
  + if err != nil && !stderrors.Is(err, syscall.ECHILD) {
  + log.L.Errorf("failed to process wait, %v", err)
  }
  }
  if err := m.mounter.Umount(d.MountPoint()); err != nil && err != syscall.EINVAL {
  