GCE: cloud-init 17.2.35 no longer processes user data

[Chad Smith]

SRU update in ubuntu Artful to cloud-init 17.2.35 breaks user-data processing on Google's cloud.

Changes that made it into this release changed how user-data is being processed and it was not being saved in the datasource's userdata. As a result custom #cloud-config is not performed on a google artful instance.

You can see instance-data is properly discovered by cloud-init, but it's not actually being saved as the user-data in the datasource by looking at the 'ds':'user-data' key in /run/cloud-init/instance-data.json.

$ cat /run/cloud-init/instance-data.json | grep user-data
   "instance-data": "{\"user-data\":\"#cloud-config\\nhostname: mybionic\\n\"}",
  "user-data": null,

We should actually see the content of user-data instead of null since instance-data has it.

This is broken on Artful and Bionic, limited to Google's cloud. It would affect xenial too if 17.2.35 publishes to xenial.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: cloud-init 18.1-0ubuntu1 [modified: usr/lib/python3/dist-packages/cloudinit/sources/DataSourceGCE.py]
ProcVersionSignature: Ubuntu 4.15.0-10.11-generic 4.15.3
Uname: Linux 4.15.0-10-generic x86_64
ApportVersion: 2.20.8-0ubuntu10
Architecture: amd64
CloudName: GCE - Google Compute Engine
Date: Thu Mar 1 22:04:45 2018
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
SourcePackage: cloud-init
UpgradeStatus: No upgrade log present (probably fresh install)
cloud-init-log-warnings: 2018-03-01 21:58:18,325 - DataSourceGCE.py[WARNING]: CHAD encoding None
user_data.txt: