Add new scenario NSPerf-RFC2544

Add new scenario NSPerf-RFC2544

List of changes:
 - Added new scenario NSPerf-RFC2544 that runs complete test per
   runner's iteration
 - NSPerf is still present for backward compatibility
 - Added ScenarioOutput class which allows scenario to report
   data (kpi,...) at any moment of time (not only once per run)
 - New output mechanism is used only by new NSPerf-RFC2544 scenario

JIRA: YARDSTICK-1592

Change-Id: Ica8078f61d895f74df90e8eaad7a675b28bd19c6
Signed-off-by: Serhiy Pshyk <serhiyx.pshyk@intel.com>