Remove all non-external networks on down.

Also moves the shutdown test fixtures to be a more general v2-full fixture.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

tests/fixtures/shutdown/docker-compose.yml

@@ -1,10 +0,0 @@
-
-version: 2
-
-volumes:
-  data:
-    driver: local
-
-services:
-  web:
-    build: .

tests/fixtures/v2-full/docker-compose.yml

@@ -0,0 +1,20 @@
+
+version: 2
+
+volumes:
+  data:
+    driver: local
+
+networks:
+  front: {}
+
+services:
+  web:
+    build: .
+    networks:
+      - front
+      - default
+
+  other:
+    image: busybox:latest
+    command: top