bug#40981: Graphical installer tests sometimes hang.

[Mathieu Othacehe]

Hello,

Graphical installer tests sometimes hang, before starting marionette
tests. See for instance:
https://ci.guix.gnu.org/log/d31s9sycixhvfak5lpzdg0mzvz5aa9av-gui-installed-os-encrypted.

Restarting tests just after a hang (on the same installed image),
sometimes work. I removed the "quiet" kernel argument to see what's
going on.

--8<---------------cut here---------------start------------->8---
[    0.862608] Freeing unused kernel image memory: 1964K
[    0.863177] Run /init as init process
GC Warning: pthread_getattr_np or pthread_attr_getstack failed for main thread
GC Warning: Couldn't read /proc/stat
Welcome, this is GNU's early boot Guile.
Use '--repl' for an initrd REPL.

loading kernel modules...
[    0.915640] usbcore: registered new interface driver usb-storage
[    0.917800] usbcore: registered new interface driver uas
[    0.919569] hidraw: raw HID events driver (C) Jiri Kosina
[    0.920519] usbcore: registered new interface driver usbhid
[    0.921177] usbhid: USB HID core driver
[    0.933506] isci: Intel(R) C600 SAS Controller Driver - version 1.2.0
[    0.951303] PCI Interrupt Link [LNKD] enabled at IRQ 11
[    0.970144] PCI Interrupt Link [LNKA] enabled at IRQ 10
[    0.974033] virtio_blk virtio1: [vda] 4505600 512-byte logical blocks (2.31 
GB/2.15 GiB)
[    0.976186]  vda: vda1 vda2

;; hanging here.
--8<---------------cut here---------------end--------------->8---

It seems that the boot freezes, soon after the initrd is started, and
before loading the boot script.

Mathieu