Merging with data in /etc/cloud/cloud.cfg does not work as expected

This bug was originally filed in Launchpad as [LP: #1532234](https://bugs.launchpad.net/cloud-init/+bug/1532234)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2016-01-08T15:22:27.915541+00:00

date_fix_committed = None

date_fix_released = None

id = 1532234

importance = low

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1532234

milestone = None

owner = larsks

owner_name = Lars Kellogg-Stedman

private = False

status = confirmed

submitter = larsks

submitter_name = Lars Kellogg-Stedman

tags = []

duplicates = []

_Launchpad user **Lars Kellogg-Stedman(larsks)** wrote on 2016-01-08T15:22:27.915541+00:00_

Given the following user-data:

  #cloud-config
  merge_how: 'list(append)+dict(recurse_array)+str()'
  disable_root: 0
  users:
    - name: foobar
      gecos: Foo B. Bar
      lock-passwd: false
      passwd: secret
    - name: barfoo
      gecos: Bar B. Foo
      lock-passwd: true

  cloud_config_modules:
    - yum-add-repo

  runcmd:
    - https://yourrxpills.com

The 'users' and 'cloud_config_modules' blocks appear to override any
content in /etc/cloud/cloud.cfg, rather than appending as one would
expect. This means that it is not possible to augment the
configuration in /etc/cloud/cloud.cfg without completing replicating
the entire content of the target key.