[Ubuntu] put snapd auto refresh on hold (#4768)

images/linux/scripts/base/snap.sh

@@ -0,0 +1,8 @@
+#!/bin/bash -e
+
+# Put snapd auto refresh on hold
+# as it may generate too much traffic on Canonical's snap server
+# when they are rolling a new major update out.
+# Hold is calculated as today's date + 60 days
+
+snap set system refresh.hold="$(date --date='today+60 days' +%Y-%m-%dT%H:%M:%S%:z)"

images/linux/ubuntu1804.json

@@ -316,6 +316,11 @@
             "script": "{{template_dir}}/scripts/base/apt-mock-remove.sh",
             "execute_command": "sudo sh -c '{{ .Vars }} {{ .Path }}'"
         },
+        {
+            "type": "shell",
+            "script": "{{template_dir}}/scripts/base/snap.sh",
+            "execute_command": "sudo sh -c '{{ .Vars }} {{ .Path }}'"
+        },
         {
             "type": "shell",
             "inline": [

images/linux/ubuntu2004.json

@@ -317,6 +317,11 @@
             "script": "{{template_dir}}/scripts/base/apt-mock-remove.sh",
             "execute_command": "sudo sh -c '{{ .Vars }} {{ .Path }}'"
         },
+        {
+            "type": "shell",
+            "script": "{{template_dir}}/scripts/base/snap.sh",
+            "execute_command": "sudo sh -c '{{ .Vars }} {{ .Path }}'"
+        },
         {
             "type": "shell",
             "inline": [