lxc-download: Bump compat to 2 after OpenSUSE

OpenSUSE is now ready for the download template in the master branch,
however it's not going to be compatible with older LXC as they lack the
needed config files, so bump the compat level to 2 to indicate that the
current lxc-download can deal with the current OpenSUSE containers.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
snapshot test: make sure that external snapshot was really created

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