Kit: Do not keep name unique during updates

Do not keep the name unique at KitModel level while applying changes.

We create temporary kits at that time which have conflicting names if
you added kits with the default name "Unnamed" before.

Task-number: QTCREATORBUG-10267
Change-Id: I42ba1299c938e1a2c1638d2669fc85ff5b6d88b5
Reviewed-by: Daniel Teske <daniel.teske@digia.com>