bug#55898: jami service failing following 'guix deploy' update

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

Hello Guix!

After having fixed the tests of the jami-service-type and pushed the fix
as 85b4dabd94d53f8179f31a42046cd83fc3a352fc, I was confident it would
work, but my freshly 'guix deploy'ed machine says otherwise:

--8<---------------cut here---------------start------------->8---
$ sudo herd stop jami
$ sudo herd start jami
Service jami-dbus-session has been started.
herd: exception caught while executing 'start' on service 'jami':
Unbound variable: jami-service-available?

$ guix system describe
Generation 141  Jun 11 2022 01:38:12    (current)
  file name: /var/guix/profiles/system-141-link
  canonical file name: /gnu/store/vx9sd4vb2yfv0zhycd461m9wfvgzclsp-system
  label: GNU with Linux-Libre 5.17.14
  bootloader: grub-efi
  root device: label: "btrfs-pool-1"
  kernel: /gnu/store/zf4062hz23485dp1xr8w6zbk2m8igpsk-linux-libre-5.17.14/bzImage
  configuration file: /gnu/store/n2wqba6npybjd8i730cpi9qc61p16jkr-configuration.scm
--8<---------------cut here---------------end--------------->8---

I don't get it; how can the service runs fine in the instrumented VMs
the system tests use, and fail in my updated machine?  Could it be a
fault in 'guix deploy'?

To be investigated...

Thanks,

Maxim