Changed apt_mk_version to proposed

Change-Id: Ieea5cf801ec13232d7b8aa11dfadfc637ebb4b1e
diff --git a/init.yml b/init.yml
index 43ce183..e47d8b1 100644
--- a/init.yml
+++ b/init.yml
@@ -39,7 +39,7 @@
 - service.docker.host
 parameters:
   _param:
-    apt_mk_version: '2018.3.1'
+    apt_mk_version: 'proposed'
     aptly_gpg_keypair_id: A8272E04
     aptly_gpg_passphrase: ""
     aptly_server_secure: true