remove etcd3 from subnode install

The stops installing etcd3 on the subnodes. In
I76f8740448b25a48869ee80006e826baa6cafc2b we make etcd3 mean that
the etcd3 server (and always install the etcd3 client).

Change-Id: I4124dc7e3fd3b4d973979da85209ec991c0f8c4b

features.yaml

@@ -213,7 +213,7 @@ primary:
 subnode:
   default:
     base:
-      services: [dstat, peakmem_tracker, etcd3]
+      services: [dstat, peakmem_tracker]
 
   ceilometer:
     base: