Reduce Linux box size by not packing a swap partition gubbish

Current boxes are redistributed with the swap partition filled by gubbish -- if clean it the box size is reduced by 100-200 MB.
One more point that there also a little bit less chance of sensitive information leakage.

* Whiteout swap partition for CentOS, Debian, Fedora, OpenSUSE, Oracle,
  RHEL, SLES, Ubuntu
* FreeBSD has no support for blkid, left it as is