Handle the enterprise field of the sflow flow and counter record format.

Handle the enterprise field of the sflow flow and counter record format.

Thanks to some traces sent my way by Gavin McCullagh, and a comparison
against the output of inMon's sflowtool, I can confidently say "Yes
Virginia, there is an enterprise other than zero."  Which means lest we
start trying to decode something as what it is not, we best actually
look at the enterprise field and make sure it is one we recognize.