Use virNetServerRun instead of custom main loop

Use virNetServerRun instead of custom main loop

The LXC controller code currently directly invokes the
libvirt main loop code. The problem is that this misses
the cleanup of virNetServerClient connections that
virNetServerRun takes care of.

The result is that when libvirtd is stopped, the
libvirt_lxc controller process gets stuck in a I/O loop.
When libvirtd is then started again, it fails to connect
to the controller and thus kills off the entire domain.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>