fix: Always use single datasource if specified (#5098)
Jira: https://issues.redhat.com/browse/RHEL-36255
This change may require a user to add `None` to the `datasource_list`
defined in `/etc/cloud/cloud.cfg[.d]` if they have a customized
datasource_list and want the DataSourceNone fallback behavior.
ds-identify would automatically append "None" to the datasource_list
if a single entry was provided in /etc/cloud/cloud.cfg[.d].
This wasn't a problem in the past as the python code would detect
a single datasource along with None as an indication to automatically
use that datasource. Since the python code no longer does that,
we should ensure that one specified datasource results in one specified
datasource after ds-identify has run.
Fixes GH-5091
(cherry picked from commit cdbbd17ae400e432d13f674c18a6f5c873fa328b)
Signed-off-by: Ani Sinha <anisinha@redhat.com>