#3 Fix for switches that report extra modules (ex C2960's)

[Ed Szynaka]

Cisco 2960's report multiple modules in the stack even though there aren't any and they also report extra items such as fans and power supplies as modules. These "modules" report to have -1 ports on them. This patch reads that data and subtracts those modules from the module count. I didn't know if other modules correctly report a port count of -1, but if not one could add a return at that point.

[Ed Szynaka]