c/r: put lxc-restore-net in /usr/share

c/r: put lxc-restore-net in /usr/share

On restore, we pass criu a script to manage the network interfaces (i.e. the
full path to lxc-restore-net), which we previously installed into
/var/lib/<tuple>/lxc. However, this is also the directory that is the default
for use in mounting the rootfs locally before pivot_root()ing. So, we mounted
the rootfs and then happliy called criu, pointing it to this directory which
didn't have lxc-restore-net any more, it just had the container's rootfs.
Instead, we should put lxc-restore-net somewhere else, so that criu can still
see it after the rootfs is mounted.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>