Add nodeid and proper secret key for corosync

The shared secret is stored in /etc.  Corosync might be required in the
bootstrapping process later, so it probably makes sense to keep it on the
filesystem outside /bitraf1.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
Added a package unpacking script

The unzip command line as a bit specialized, so it's better not having to
remember it.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>