Switch nova-baremetal-deploy-helper to use sfdisk.

This patch changes make_partitions function to use sfdisk instead
of fdisk. Also added logging of cmd, stdout, and stderr should
command fail.

Fixes Bug 1088652

Change-Id: Ia2711a5450900c95598253f2a7b02e7c3e83a3d8
Authored-by: Chris Krelle <nobodycam@gmail.com>
Merge "Switch nova-baremetal-deploy-helper to use sfdisk."