(maint) Remove unsupported platforms

This commit removes logic for handling platforms no longer supported by
puppet-agent, Ubuntu 14.x and Ubuntu on PowerPC.

acceptance/tests/selinux.rb

@@ -4,7 +4,7 @@
       'audit:acceptance'
 
   confine :to, :platform => /el-|fedora-|debian-|ubuntu-/
-  confine :except, :platform => /ubuntu-.*-ppc64el|ubuntu-14|el-6/
+  confine :except, :platform => /el-6/
 
   require 'puppet/acceptance/common_utils'