libfdisk: add fdisk_wipe_partition()

libfdisk: add fdisk_wipe_partition()

Now libfdisk provides functionality wipe disk device only ([s]fdisk
option --wipe).

This patch allows to probe for filesystems/RAIDs on newly created
partitions.  It means we can remove signatures before the partition
node (device) is created. This reduces udev events and it's
unnecessary to call wipefs for all partitions.  For example

  sfdisk --wipe=always --wipe-partitions=always /dev/sda <<<
  ...
  EOF

is a elegant way how to create new disk layout without any obsolete
filesystems/RAIDs.

Signed-off-by: Karel Zak <kzak@redhat.com>