Get rid of fundamentally broken disk allocation code.

This gets rid of the broken code that assumes that /dev/sda is always
the boot device, and adds a mechanism to allow individual barclamps to
claim a physical device in a fashion that should be relatively portable.
Merge pull request #119 from VictorLowther/pull-req-release-pebbles-master-b33d4f791a3432f0d3d2d4ea58a1c80f9ce6c95e

https://github.com/crowbar/barclamp-deployer/pull/119

Merged by devtool for cloudsleuth