pve6to7: storage content: ignore misconfigured unreferenced volumes

pve6to7: storage content: ignore misconfigured unreferenced volumes

If the same local storage is configured twice with content type
separation, migration in PVE 6 would lead to the volumes being
duplicated. As that would happen for every migration, such an issue
would likely be noticed already, and in PVE 7 such configuration is
not problematic for migration anymore. Also, misconfigured
unreferenced volumes are not an issue with respect to the upgrade
itself, just drop the check.

It's not necessary to scan storages with either 'images' or 'rootdir'
anymore, as only the log_info() remains.

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
(cherry picked from commit 5dc51df910620a47459228e05675c2af81cbc46d)
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>