This update for dkimproxy fixes the following issues:

- Fix possible symlink attack in /run/dkimproxy/sysconfig
  (boo#1217173)
  Remove environment variables DKIMPROXY_USER DKIMPROXY_GROUP.
  These are hardcoded anyway in dkimproxy-tmpfiles. Changing these
  would only lead to trouble. Now User and Group in dkimproxy-in.service
  are set to dkim to avoid the mentioned security issue.
  ExecStart got a '+' to execute it by root rights.

- Fix ExecStartPre path. This changes depending on %_libexecdir macro. 
  Problem was mentioned in (boo#1217173)

- Follow-up fix for boo#1216919
  * make sure dkimproxy-in works even when the dynamically-created
    config file under /run does not exist 

- Fix boo#1216919 
  * use the correct env var for the hostname