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.
This doesn't quite work as it's not using bundler_ext.. I'm also a little worried that it'll create a .lock file if we did fix it.  I'd suggest doing a gem list inside the SCL instead for safety's sake.