Global Zone Memory Support

The plugin check_mem works great in smartmachines (zones) but unfortunately not on a physical smartos (global zone). I patched the plugin, so the plugin also works on a global zone. Unfortunately it's much more complicated on a global zone because kstat does not show all necessary information. 

There might be much better solutions how to accomplish this, but even though several commands are used to obtain all necessary information on the global zone, it works and it's sufficiently fast (0.1s).