Fix the behaviour of the default value for report server

The default behaviour for the reportserver value should be $server not
''.

Author: Stephen

manifests/agent.pp

@@ -55,7 +55,7 @@
   $ordering               = undef,
   $trusted_node_data      = undef,
   $listen                 = false,
-  $reportserver           = undef,
+  $reportserver           = '$server',
 ) inherits puppet::params {
 
   if ! defined(User[$::puppet::params::puppet_user]) {