Fix OpenSUSE installation issues

OpenSUSE runs a script which builds the main.cf file automatically if a file
doesn't exist. This breaks idempotency so go ahead and touch the file via Chef.

In addition, postfix is built with incorrect default settings for `setgid_group`
and `daemon_directory`, so set it properly in the config.

Signed-off-by: Lance Albertson <lance@osuosl.org>

attributes/default.rb

@@ -105,6 +105,9 @@ when 'rhel'
   default['postfix']['cafile'] = '/etc/pki/tls/cert.pem'
 when 'amazon'
   default['postfix']['cafile'] = '/etc/pki/tls/cert.pem'
+when 'suse'
+  default['postfix']['main']['setgid_group'] = 'maildrop'
+  default['postfix']['main']['daemon_directory'] = '/usr/lib/postfix/bin'
 else
   default['postfix']['cafile'] = "#{node['postfix']['conf_dir']}/cacert.pem"
 end