When we read a lxc.network.hwaddr line, if it contained any 'x's then
those get quitely filled in at config_network_hwaddr.  If that happens
then we want to save the autogenerated hwaddr in the unexpanded config
so that when we write it to disk, it is saved.

This patch dumbly re-generates the network configuration in the
unexp configuration every time we load a config file, just as we do
after every clone.
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>