`qvm.prefs` Salt module makes changes while in test mode

[andrewdavidwong]

Reported by user sn3dweog on qubes-users.

Qubes OS release

R4.2.1

Brief summary

The qvm.prefs Salt module makes changes while in test mode.

Steps to reproduce

qvm-create --label red my-new-qube
qvm-prefs my-new-qube default_dispvm whonix-ws-dvm
sudo qubesctl qvm.prefs my-new-qube default_dispvm='' test=true
qvm-prefs my-new-qube default_dispvm

Expected behavior

"whonix-ws-dvm" printed.

Actual behavior

"" printed.

Notes

Tested on qubes-mgmt-salt-dom0-qvm 4.2.1-1.