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>

recipes/_common.rb

@@ -42,6 +42,8 @@ when 'rhel', 'fedora', 'amazon'
     notifies :start, 'service[postfix]'
     not_if '/usr/bin/test /etc/alternatives/mta -ef /usr/sbin/sendmail.postfix'
   end
+when 'suse'
+  file '/var/adm/postfix.configured'
 when 'omnios'
   manifest_path = ::File.join(Chef::Config[:file_cache_path], 'manifest-postfix.xml')