ubuntu: Various fixes

 - Drop disabled entries from allowed devices list
 - Improve generated config layout a bit
 - Drop redundant uname call
 - Re-generate the SSH host keys on container creation

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
python: Fix get_ips and nesting with lxcpath

When using -P (lxcpath), the parameter path needs to be forwarded
to the various commands being run but not used by the nested lxc-ls
as it's relatively unlikely that both the host and the nested containers
use a custom path.

This isn't ideal but short of having a way to provide the container path
for every single of the nesting (with potential unlimited depth), it's
the best we can do.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>