Add element to disable cloud-init resizefs

The resize module is problematic for using grub on very large root
partitions. It is also extremely slow on large partitions, and users are
likely better off creating new partitions in the empty space.

Change-Id: Ic050c74aa71165b43c8908c4d6c7c0ea99ddafa3
Story: 2000175

elements/cloud-init-disable-resizefs/README.rst

@@ -0,0 +1,7 @@
+Disable cloud-init's resizefs module
+------------------------------------
+
+The cloud-init resizefs module can be extremely slow and will also
+unwittingly create a root filesystem that cannot be booted by grub if
+the underlying partition is too big. This removes it from cloud.cfg,
+putting the onus for resizing on the user post-boot.

elements/cloud-init-disable-resizefs/post-install.d/50-cloud-init-disable-resizefs

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+if [ ${DIB_DEBUG_TRACE:-1} -gt 0 ]; then
+    set -x
+fi
+set -eu
+set -o pipefail
+
+sed -ie 's/^ - resizefs$//' /etc/cloud/cloud.cfg