Goal: 

The must-gather-openstack tool used to gather RHOSO information from the OCP cluster should store `version` file in the archive. Guidelines about what this file should contain are in the https://github.com/openshift/must-gather/blob/master/must-gather.md#must-gather-images

This will be useful to autodiscover used must-gather context in the `ccx-ocp-core` tool used by the `insights` tool to analyse must-gather archives. See parent issue for more details OSPRH-11236

Acceptance Criteria:

Archive collected by the `must-gather` tool using `must-gather-openstack` image should contain proper `version` file in the root directory of the archive.