Don't add the testing "webcam" device,
which is unexpected to see when querying
what devices fwupd believes exist :).
Won't change behavior for anyone defining
the blacklistPlugin option already,
but doesn't seem worth making more complicated.
We override the ESP mount point in the config file /etc/fwupd/uefi.conf
(available since version 1.0.6), as it is set to a path in the nix store
during build time.
Tests are disabled as it needs /etc/os-release, which is not available
when building with sandboxing enabled.
