Use DiskPartitioner

Use the new DiskPartitioner class to create the partition layout.

This commit also moves the sleep() workaround to avoid the "device is
busy" problem into the DiskPartitioner wrapper.

Change-Id: I28bb17c7ce2262d3088f58ab4421145e8d9baa1f
Closes-Bug: #1297925
Merge "Use DiskPartitioner"