BugLink: https://bugs.launchpad.net/bugs/1891224

Update the systemd service for the fcopy daemon and add a new udev
rule to ensure the service will not fail in case fcopy is not enabled
for the guest.

The udev rules is responsible for starting the service only when the
fcopy device is available. In the unit file, the service is now bound
to the device unit, so the service can be stopped if the device is
removed. And the service is also conditioned to the existence of the
device, this way we avoid starting and stopping the service during
boot if the device is not available.
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>