Disable snapd.refresh.service on 16.04 to speed up boot (no snap packages in use)

There's no need to disable it to speed up the boot. This was a mistake on our part, and has been fixed in 2.11, out for updating in the next couple of days. Here is the full change log:

https://github.com/snapcore/snapd/blob/2.11/debian/changelog

According to the systemd wiki, the command to disable a service and prevent it from starting at bootup is:

sudo systemctl disable [foo]

so

sudo systemctl disable snapd.refresh.service

should work in this instance.