Fix the integration test healthcheck

The alpine nginx container doesn't contain curl, so let's override the
healthcheck command to use wget.

test/integration/docker/deployer/app/config/deploy.yml

@@ -10,5 +10,4 @@ registry:
 builder:
   multiarch: false
 healthcheck:
-  path: /
-  port: 80
+  cmd: wget -qO- http://localhost > /dev/null