virtiofsd: do not break or replace qemu-system-common

The whole point of having virtiofsd is to share directories between qemu host and guests, so we shouldn't uninstall qemu when virtiofsd is installed.

This is an alternative implementation of the virtio-fs protocol, qemu provides its own implementation in /usr/lib/qemu/virtiofsd, we can simply install rust-virtiofsd in /usr/libexec/virtiofsd (like any other daemons) and co-exist with qemu's virtiofsd.

Signed-off-by: Andrea Righi andrea.righi@canonical.com