ipmitool default interface

[Vernon Mauery]

I have seen several requests for help on this list that could have been 
avoided if the BMC internal ipmitool used dbus as its default interface. 

I do not think we are quite ready to upstream this commit or the actual 
interface, since the dbus interface will be changing as part of the 
refactor of ipmid's architecture. But for now, it makes sense to set the 
default interface as dbus.

After I have finished working on the refactor, I will push the changes 
upstream and then we should be able to just run with a standard 
cross-compiled build of ipmitool.

--Vernon