wipe_lv: use zeroing ioctl only for large sizes

wipe_lv: use zeroing ioctl only for large sizes

There is no easy way to detect, whether device supports zeroing,
and kernel also zeroes device when it's not directly supported,
but with extra message:

operation not supported error, dev X, sector Y op 0x9:(WRITE_ZEROES)...

So to avoid generating such message with every 'lvcreate', use for
zeroing of upto 8K just standard write of zeroed page.
(maybe we can go with even larger sizes).