cc_puppet: support AIO installations and more

[GabrielNagy]

Proposed Commit Message

cc_puppet: support AIO installations and more

- update the puppet module to support AIO installations by setting
  `install_type` to `aio`
- make the install collection configurable through the `collection`
  parameter; by default the rolling `puppet` collection will be used,
  which installs the latest version)
- when `install_type` is `aio`, puppetlabs repos will be purged after
  installation; set `cleanup` to `False` to prevent this
- AIO installations are performed by downloading and executing a shell
  script; the URL for this script can be overridden using the
  `aio_install_url` parameter
- make it possible to run puppet agent after installation/configuration
  via the `exec` key
- by default, puppet agent will run with the `--test` argument; this can
  be overridden via the `exec_args` key

Additional Context

This was requested on a ticket in the Puppet JIRA: https://tickets.puppetlabs.com/browse/PUP-10926.
The plan is to sign the CLA as an organization, but I opened the PR early to get some review if possible.

Test Steps

Apart from unit tests, I used an Ubuntu 18.04 machine with QEMU to validate the module functionality; used the following to replace the puppet module and restart the VM:

virsh shutdown bionic
sleep 1
rm snapshot.img
qemu-img create -f qcow2 -b bionic-server-cloudimg-amd64.img snapshot.img
virt-copy-in -a snapshot.img ~/prepo/cloud-init/cloudinit/config/cc_puppet.py /usr/lib/python3/dist-packages/cloudinit/config
cloud-localds user-data.img user-data
virsh start bionic

Checklist:

• My code follows the process laid out in the documentation
• I have updated or added any unit tests accordingly
• I have updated or added any documentation accordingly

[GabrielNagy]

Update: Puppet Labs has signed the Canonical CLA as an organization

[GabrielNagy]

Hey @TheRealFalcon, it'd be great to get this reviewed/merged. We validated this internally and everything works as expected, let me know if there's anything else I can do to get the PR merged! Thanks! 😄

[TheRealFalcon]

Thanks for the submission. Overall this change is good. I left some comments inline, but most are fairly minor.

I noticed that the CLA has been signed on behalf of the company, but additionally any contributor needs to be added (alphabetically) to the CLA signers file. The full details are described in the last bullet point of the documentation. Currently you only need to add yourself, but feel free to add the other puppet contributors if you have them.

[TheRealFalcon]

Thanks!