added group docker for user rundeck

linux states tries to create runbook user before docker is installed, so its failling

Change-Id: I616777311f8cde52d0670df102460c9fd124b503
diff --git a/rundeck/client/runbook.yml b/rundeck/client/runbook.yml
index a41481a..773673b 100644
--- a/rundeck/client/runbook.yml
+++ b/rundeck/client/runbook.yml
@@ -13,6 +13,10 @@
             - docker
           full_name: Rundeck Remote
           home: /var/lib/runbook
+      group:
+        docker:
+          enabled: true
+          name: docker
   openssh:
     server:
       enabled: true