Set legacy_debian_symlinks to true

After update nodejs from system to 6.x in patch[1],
ubuntu xenial nodejs related files will be link to a loop:
/usr/local/bin/node -> /usr/bin/nodejs
/usr/bin/node -> /usr/bin/nodejs
/usr/bin/nodejs -> /etc/alternatives/nodejs
/etc/alternatives/nodejs -> /usr/bin/node

Also, in openstack-infra/system-config, the code we have for
etherpad node can't bringup one, we should remove the node
'Node-OS: xenial' that may misslead others

This patch is aimed to help etherpad node's system upgrade
to xenial.

[1] Ied9e5bd7ffa16f1832d3e1e26d0886de67f98f72

Change-Id: I6f7d50bed470916f7b150785ef68d34f336cb0ce

manifests/init.pp

@@ -59,8 +59,9 @@ class etherpad_lite (
 
   if ($nodejs_version != 'system') {
     class { '::nodejs':
-      repo_url_suffix => $nodejs_version,
-      before          => Anchor['nodejs-package-install'],
+      repo_url_suffix        => $nodejs_version,
+      legacy_debian_symlinks => false,
+      before                 => Anchor['nodejs-package-install'],
     }
   } else {
     package { ['nodejs', 'npm']: