Virtual machine password via ConfigDrive

The ConfigDrive metadata provider delivers the virtual machine password simultaneously in two variants, leaving which one to use to the user discretion:

1. As the ``<mountdir>/cloudstack/password/vm_password.txt`` file.

This file is intended to be used by an external script that runs inside the virtual machine every boot, and changes the password if needed.

The init-script that implements this functionality can be found in the `Cloudstack source <https://github.com/apache/cloudstack/blob/main/setup/bindir/cloud-set-guest-password-configdrive.in>`_.

.. note::

The ``vm_password.txt`` file is not compatible with cloud-init password module, so the cloud-init will ignore it.

It is up to Cloudstack administrator to include the script processing it in the virtual machines and/or their templates.

2. As the ``<mountdir>/openstack/latest/vendor_data.json``.

This is a standard password location supported by cloud-init's both ConfigDrive datasource and the password module.

Therefore, this variant allows using cloud-init as the only tool for provisioning a virtual machine, without using external scripts.

.. warning::

Cloud-init password module is designed to only perform the initial virtual machine password setup.

It will ignore the changes in ``vendor_data.json`` after the first run. Therefore, resetting the virtual machine password from Cloudstack will not work with this variant.