Merge pull request #405 from gravitational/sergei/wait_for_readyness_…

…gravity_site_55x

[5.5.x] Use postUpdate hook to check gravity site status after upgrade

assets/site-app/images/hook/entrypoint.sh

@@ -1,5 +1,5 @@
 #!/bin/sh
-set -e
+set -ex
 
 echo "Assuming changeset from the environment: $RIG_CHANGESET"
 # note that rig does not take explicit changeset ID

assets/site-app/resources/app.yaml

@@ -25,6 +25,22 @@ hooks:
               - name: hook
                 image: site-app-hook:0.0.1
                 args: ["update"]
+  postUpdate:
+    job: |
+      apiVersion: batch/v1
+      kind: Job
+      metadata:
+        name: site-app-post-update
+      spec:
+        template:
+          metadata:
+            name: site-app-post-update
+          spec:
+            restartPolicy: OnFailure
+            containers:
+              - name: post-update-hook
+                image: quay.io/gravitational/debian-tall:stretch
+                command: ["/opt/bin/gravity", "site", "status"]
   rollback:
     job: |
       apiVersion: batch/v1