Revert "Added Percentage Free Memory Stats (#3472)" (#3540)

This reverts commit 62902aa.

Author: truthbk

checks/system/unix.py

@@ -407,7 +407,6 @@ def check(self, agentConfig):
 
                 if memData['physTotal'] > 0:
                     memData['physPctUsable'] = float(memData['physUsable']) / float(memData['physTotal'])
-                    memData['physPctFree'] = float(memData['physFree']) / float(memData['physTotal'])
             except Exception:
                 self.logger.exception('Cannot compute stats from %s', proc_meminfo)