lxc: Don't reboot host on virDomainReboot

If the container is really a simple one (init is just bash and
the whole root is passed through) then virDomainReboot and
virDomainShutdown will talk to the actual init within the host.
Therefore, 'virsh shutdown $dom' will result in shutting down the
host. True, at that point the container is shut down too but
looks a bit harsh to me.

The solution is to check if the init inside the container is or
is not the same as the init running on the host.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>