don't use a hardcoded concatdir

Get the concat base directory from a fact -> makes it useable if
Puppet's :vardir is not /var/lib/puppet/. This fixes problems with
PE and makes the module also useable for puppet runs as
unpriviledged user.

lib/facter/concat_basedir.rb

@@ -0,0 +1,5 @@
+Facter.add("concat_basedir") do
+    setcode do
+        File.join(Puppet[:vardir],"concat")
+    end
+end

manifests/setup.pp

@@ -14,7 +14,7 @@
 # It also copies out the concatfragments.sh file to /usr/local/bin
 class concat::setup {
     $root_group = 0
-    $concatdir = "/var/lib/puppet/concat"
+    $concatdir = $concat_basedir
     $majorversion = regsubst($puppetversion, '^[0-9]+[.]([0-9]+)[.][0-9]+$', '\1')
 
     file{"/usr/local/bin/concatfragments.sh":