Update blocky one instance at a time

Avoids dns going down with all instances updating at once

blocky/blocky.nomad

@@ -6,6 +6,11 @@ variable "config_data" {
 job "blocky" {
   datacenters = ["dc1"]
   type = "system"
+  priority = 100
+
+  update {
+    max_parallel = 1
+  }
 
   group "blocky" {