Add temporary_enable_v2 flag to cc-worker config (#4067)

* required for #4058

Author: jochenehret

lib/cloud_controller/config_schemas/base/worker_schema.rb

@@ -21,6 +21,8 @@ class WorkerSchema < VCAP::Config
             default_health_check_timeout: Integer,
             maximum_health_check_timeout: Integer,
 
+            optional(:temporary_enable_v2) => bool,
+
             uaa: {
               internal_url: String,
               optional(:ca_file) => String,