Renames snapshot 'pre-installed' on controller node

Renames snapshot 'pre-installed' to 'openstack-controller_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: I1c9ce714955dec66c9979ac8a86c38d703017f9c
Merge "Renames snapshot 'pre-installed' on controller node"