lxd/device/disk: Switch to using DiskVMVirtfsProxyStart for VM 9p proxy
lxd/device/disk: Switch to using DiskVMVirtfsProxyStart for VM 9p proxy

This utilises socket file descriptors rather than socket paths, so no need to wait for the path to appear or clean it up now.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

hallyn/lxd,hallyn/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd