Choose configuration directory

Choose configuration directory

Maybe it will be more logical to keep configs into /etc/lxc/?

Or, maybe, just use --with-config-path=/some/path switch into configure,
which could be overridden as user wants to? Something like this one (in
assumption, that this is up to user to create corresponding directory):

Signed-off-by: Andrian Nord <NightNord@gmail.com>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>