Generate localhost only inventory if not a nodepool node
Generate localhost only inventory if not a nodepool node

Before this change the inventory generator macro requires the existence
of the /etc/nodepool data to populate the ansible inventory. This change
makes it so that if the /etc/nodepool directory doesn't exist, we create
a localhost only inventory file with no nodepool data.

CiscoSystems/project-config-third-party,CiscoSystems/project-config-third-party