bug#33362: System tests stuck in "shepherd[1]: waiting for udevd..."

[Mark H Weaver]

In recent evaluations of 'master', there have been two more instances of
this problem occurring, on x86_64 and i686:

  https://hydra.gnu.org/build/3252398  (from eval 110355, commit 08861d25)
  https://hydra.gnu.org/build/3225361  (from eval 110351, commit 69f867b1)

I aborted these jobs.

      Mark