Bug#944860: udevadm trigger fails in chroot

[Jonah Brüchert]

Thanks for looking into the issue.

> Can you be more specific how you setup your chroot so we have a chance
> to reproduce the problem?

The exact setup is a little more complicated.

The chroot is created using debos, which if I remember correctly uses a
chroot inside qemu if that's relevent.

The exact command is `./bin/debos-docker -t variant:plasma-mobile
halium.yml`, ran inside the following git repository:
https://gitlab.com/debian-pm/tools/rootfs-builder-debos.

Whether debos-docker or a normal debos package / binary is used should
not matter, since the build process always happens inside a virtual machine.

After slightly looking into the debos source code it seems also possible
that it uses a systemd-spawn container in some cases
(https://github.com/go-debos/debos/blob/2764eed783b1b0ffb5d09f796338f09a4e2594b6/commands.go#L15)

The ci log can be found here in case useful:
https://travis-ci.com/debian-pm-tools/rootfs-builder-debos/jobs/257249532#L7353.


As reduced test case the following debos recipe could be used to save
some time:

`debos testcase.yml --debug-shell`


testcase.yml:

```

architecture: amd64

actions:
   - action: debootstrap
     suite: unstable
     components:
       - main
     mirror: https://deb.debian.org/debian
     variant: minbase

   - action: apt
     packages: [ udisks2 ]

```