Data Preservation

Currently Fuel performs full re-provisioning while performing rollback which
implies data deletion. For instance, it doesn't preserve virtual machine
image files, compute node log files, database files. That said it loses
valuable data during rollback.

The idea is to preserve certain partitions on the nodes during rollback while
fully reformat others. For instance, keep partition /var/lib/nova/instances
intact but create fs on / from the scratch.

The alternative approach would be copying valuable data back and forth before
and after the rollback. But that would drastically increase time needed for
rollback.