Renames 'pre-installed' on network node

Renames snapshot 'pre-installed' to 'openstack-network_installed'
which is more accurate description for the snapshot.

This snapshot can be used to revert back to stable functioning
controller node, which ready and does not require any further
installation or configuration.

Change-Id: I438b03c29ec4ba285a43abb184d59f40bd73d8f4
Merge "Renames 'pre-installed' on network node"