checkpoint of contianer with userns is not working

```
$ sudo bin/podman run -d --name test --uidmap 0:0:1000 quay.io/libpod/testimage:20221018 top
fcfc957177dec9a4ae308ad79713bb2a1b5598af76f1d128b24b576ad0a90021
$ sudo bin/podman container checkpoint test
2023-05-08T12:49:06.173711Z: CRIU checkpointing failed -52. Please check CRIU logfile /var/lib/containers/storage/overlay-containers/fcfc957177dec9a4ae308ad79713bb2a1b5598af76f1d128b24b576ad0a90021/userdata/dump.log
Error: `/usr/bin/crun checkpoint --image-path /var/lib/containers/storage/overlay-containers/fcfc957177dec9a4ae308ad79713bb2a1b5598af76f1d128b24b576ad0a90021/userdata/checkpoint --work-path /var/lib/containers/storage/overlay-containers/fcfc957177dec9a4ae308ad79713bb2a1b5598af76f1d128b24b576ad0a90021/userdata fcfc957177dec9a4ae308ad79713bb2a1b5598af76f1d128b24b576ad0a90021` failed: exit status 1
```

Relevant line from the log:
`(00.120964) Error (criu/mount.c:753): mnt: 2049:./dev/urandom doesn't have a proper root mount`
Full log: [dump.log](https://github.com/containers/crun/files/11421245/dump.log)

When the --uidmap argument is not used it works correctly, it works with runc but there is still a podman bug: https://github.com/containers/podman/issues/18502

```
$ crun --version
crun version 1.8.4
commit: 5a8fa99a5e41facba2eda4af12fa26313918805b
rundir: /run/user/1000/crun
spec: 1.0.0
+SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +LIBKRUN +WASM:wasmedge +YAJL
```