ceph-disk: Write 10M to all partitions before zapping

ceph-disk: Write 10M to all partitions before zapping

By writing 10M of zeroes to each partition of the device we prevent that
old data causes troubles if exactly the same partition scheme is created
on the disk again and is read by the OSD.

This mainly involves the OSD's journal which will contain data from the
previous OSD and results in a assert of the OSD.

Fixes: http://tracker.ceph.com/issues/18962
Signed-off-by: Wido den Hollander <wido@42on.com>