pegasus-integrity-check to log integrity data in monitord parseable event

In the pegasus transfer output when integrity check is computed or checked against, we need to log the timing information on the stdout in a monitord parseable format.

@@@PEGASUS_MONITORING_PAYLOAD - START @@@
{
     "ts": 1437688574,
     "monitoring_event": "int.metric",
     "payload": [
       {
         "event":"check|compute",
         "file_type": "input|output",
         "count" : number of files of type checked or computed,
         "duration": total sum in seconds,
       }
      ]
}
@@@PEGASUS_MONITORING_PAYLOAD - END @@@

In the case, where we have in same invocation checks and computes, we will have multiple JSON elements in payload list