wrappers: only fail when stopping a service if it actually is still running

[Meulengracht]

I've seen this atleast once in salesforce tickets, and recently experienced it myself. This effectively blocks removal of some snaps in very specific cases.

For instance take the fwupd snap:

philip@fadekraft-xps:~/Work/snapd/wrappers$ snap remove fwupd
error: cannot perform the following tasks:
- Stop snap "fwupd" services (systemctl command [stop snap.fwupd.fwupd.service] failed with exit status 5: stderr:
Failed to stop snap.fwupd.fwupd.service: Unit snap.fwupd.fwupd.service not loaded.)

I have fwupd installed as both a deb and a snap, and this causes systemctl to always return an issue when manipulating the service units for the snaps, as the deb package one loads first and is actually running. The error that systemctl reports is that two units are conflicting for dbus namespace registration.

[bboozzoo]

Thanks