[cups] hold-new-jobs not working

[Julian Bradfield]

On a laptop running Xubuntu 20.04 and CUPS 2.3.1, I've configured my
networked laserprinter successfully.

I want to be able to hold all jobs (because I'm going to be accepting
jobs from a bunch of other devices and passing them on), but this
doesn't seem to work.

If I do

cupsdisable --hold -Plex

and then submit a print job using lpr, I get a desktop notification
that says "Printer Error: Hold-New-Jobs", but then the job prints
anyway.

The access log shows Hold-New-Jobs successful=ok followed by
Create-Job successful-ok and Send-Document successful=ok