fixes #5928 - added selinux info to foreman-debug

I also fixed few minor issues. Tested, I uploaded run with this patch applied
so you can investigate the result directly:

```
 HOSTNAME: nightly.zzz.lan
       OS: redhat
  RELEASE: CentOS release 6.5 (Final)
  FOREMAN: 1.6.0-develop
     RUBY: ruby 1.8.7 (2011-06-30 patchlevel 352) [x86_64-linux]
   PUPPET: 2.7.25
  DENIALS: 290


A debug file has been created: /tmp/foreman-debug-08R0u.tar.xz (143452 bytes)

You may want to upload the tarball to our public server via rsync. There is a
write only directory (readable only by Foreman core developers) for that. Note
the rsync transmission is UNENCRYPTED:

  rsync /tmp/foreman-debug-08R0u.tar.xz rsync://theforeman.org/debug-incoming
```

We now list number of denials in the summary, audit.log is added, AVC lines are
also added and if audit2allow is installed we have that too.