Change getBareMetalInstances call to getHardware

Per a ticket with softlayer because their API was returning an empty array to calls to getBareMetalInstances:
The code you are using is correct. The empty array is correct as well. You do not have any machines flagged as a Bare Metal Instance. We used to refer to physical machines as Bare Metal Dedicated (monthly) and Bare Metal Instance (hourly). Now we refer to them as Bare Metal (monthly) and Bare Metal hourly (hourly). The getBareMetalInstances function will still return the hourly. Since your machines are all monthly, the empty string is correct.

getHardware gets both according to Softlayer.