Debian stretch in default configuration calls apt-get update every 24h.
And additionally, have automatic unattended security updates enabled.
Generally it would be good thing on standalone system, but in AppVM
which loose its rootfs changes after restart it is a waste of resources.
Especially when it kicks in on multiple VMs simultaneously, while on
battery (apt-daily.service have ConditionACPower=true, but VM don't have
that information...).
It would make some sense on TemplateVM/StandaloneVM, but then it kicks
in just at VM startup. Which conflicts with starting the update manually
then (by clicking "update VM" button in manager for example, or using
salt).
So, disable this feature completely.
The actual solution is based on pkg-manager-no-autoupdate by @adrelanos.
FixesQubesOS/qubes-issues#2621
