diskmanage: add wipe_blockdev method

diskmanage: add wipe_blockdev method

based on the wipe_disks method from pve-manager's Ceph/Tools.pm with the
following main differences:
    * use wipefs to wipe labels first (to avoid sgdisk complaining about the
      backed up GPT structure on a subsequent GPT initialization)
    * only take one device as an argument
    * do not use an absolute path for 'dd'
    * die if one of the command fails

The wipefs command makes checks and complains about e.g. mounted or active
devices. One could supply --force to wipefs, but in many such situations it
does not work as expected, because the device would still be detected as in-use
afterwards, and further manaual steps would be needed.

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>