fix nil reference when no network option

fixed #49

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
use default ip for nfs/ssh when no configuration

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
Merge pull request #70 from miurahr/fix_nil_options_has_key

fix nil reference when no network option