Streamline kernel config and add more hypervisors

Added driver support for all the hypervisors that have kernel support.
Also cleaned out a lot of options we didn't really need.

Change-Id: I6b58ee603606e8729482f78d55457dd9aa039731
Fix hard drive naming for Xen PV mode

It's xvdY, not xdY.

Change-Id: Id3cb2a37a045f791abbde63201f5f544f78117cc