move default network definitions up to [global] section

The keys 'cluster network' and 'public network' should
be part of [global] section.

Signed-off-by: Danny Al-Gaaf <d.al-gaaf@telekom.de>
ceph_conf_spec.rb: add missing linebreak

Signed-off-by: Danny Al-Gaaf <d.al-gaaf@telekom.de>