In cfgupgrade, we need to extract parts of and build new version numbers.

Reviewed-by: iustinp

Reviewed-by: iustinp

The whole Ganeti cluster has a single SSH key. Its fingerprint is
written to Ganeti's known_hosts file, together with an alias. This
allows us to always use that alias instead of the real hostname,
making management of the known_hosts file much easier.

This patch does not handle an upgrade from an earlier version.

Reviewed-by: ultrotter

Reviewed-by: iustinp

Reviewed-by: iustinp

Reviewed-by: schreiberal

Reviewed-by: iustinp