docker.pp: Umstellung auf Package docker-ce, FIX

manifests/docker.pp

-# Installs Docker repository, docker-engine, docker-compose
+# Installs Docker repository, docker-ce, docker-compose
 class ubuntu_server::docker($docker_compose_latest_version='1.11.2') {
     File{
         owner => 'root',
@@ -29,7 +29,7 @@ class ubuntu_server::docker($docker_compose_latest_version='1.11.2') {
 
     package{'lxc-docker':
         ensure => purged,
-        before => Package['docker-engine'],
+        before => Package['docker-ce'],
     }
 
     package{'docker-ce':