default to containerd in docker-compose

since we're going to default to using containerd in 7.1.0, we should
probably be developing against it!

this commit uses the containerd runtime by default, and replaces the
containerd override with a guardian one

Signed-off-by: Aidan Oldershaw <aoldershaw@pivotal.io>

docker-compose.yml

@@ -48,6 +48,8 @@ services:
     volumes: ["./hack/keys:/concourse-keys"]
     stop_signal: SIGUSR2
     environment:
+      CONCOURSE_RUNTIME: containerd
+
       CONCOURSE_TSA_PUBLIC_KEY: /concourse-keys/tsa_host_key.pub
       CONCOURSE_TSA_WORKER_PRIVATE_KEY: /concourse-keys/worker_key
 
@@ -61,4 +63,4 @@ services:
       CONCOURSE_BAGGAGECLAIM_DRIVER: overlay
 
       # work with docker-compose's dns
-      CONCOURSE_GARDEN_DNS_PROXY_ENABLE: "true"
+      CONCOURSE_CONTAINERD_DNS_PROXY_ENABLE: "true"

hack/overrides/containerd.yml

@@ -1,13 +0,0 @@
-# containerd.yml - a docker-compose override that makes `worker` use containerd
-#
-# ref: https://containerd.io
-# ref: https://github.com/concourse/concourse/issues/4783
-#
-version: '3'
-
-services:
-  worker:
-    environment:
-      CONCOURSE_RUNTIME: containerd
-      CONCOURSE_GARDEN_DNS_PROXY_ENABLE: ~
-      CONCOURSE_CONTAINERD_DNS_PROXY_ENABLE: "true"

hack/overrides/guardian.yml

@@ -0,0 +1,12 @@
+# guardian.yml - a docker-compose override that makes `worker` use guardian as
+# a container runtime
+#
+#
+version: '3'
+
+services:
+  worker:
+    environment:
+      CONCOURSE_RUNTIME: guardian
+      CONCOURSE_CONTAINERD_DNS_PROXY_ENABLE: ~
+      CONCOURSE_GARDEN_DNS_PROXY_ENABLE: "true"