Set run_start property using most recent packet's time

When setting the initial value for the run_start property, use the time
from the most recently received packet instead of the current system
time.  (Doesn't matter too much when using actual live data, but when
replaying old data it makes a lot more sense.)

Refs #6235

Code/Mantid/Framework/DataHandling/src/SNSLiveEventDataListener.cpp

@@ -349,7 +349,7 @@ namespace DataHandling
       // then we can initialize our workspace.  Otherwise, we'll just wait.
       if (m_instrumentName.size() > 0)
       {
-        initWorkspace();
+        initWorkspace( pkt);
       }
     }
 
@@ -370,7 +370,7 @@ namespace DataHandling
       // we can create our workspace.  Otherwise, we'll just wait
       if (m_instrumentXML.size() > 0)
       {
-        initWorkspace();
+        initWorkspace( pkt);
       }
     }
 
@@ -708,7 +708,7 @@ namespace DataHandling
   }
 
 
-  void SNSLiveEventDataListener::initWorkspace()
+  void SNSLiveEventDataListener::initWorkspace(const ADARA::Packet &pkt)
   {
     // Use the LoadEmptyInstrument algorithm to create a proper workspace
     // for whatever beamline we're on
@@ -735,6 +735,17 @@ namespace DataHandling
     prop = new TimeSeriesProperty<int>(SCAN_PROPERTY);
     m_buffer->mutableRun().addLogData(prop);
 
+    // We must always have a run_start property or the LogManager throws an
+    // exception.  The "real" value will come from a RunStatus packet saying that
+    // a new run is starting.  Until we get one of those packets, we'll just use
+    // the time from the packet.  (In a truely "live" stream, current time would
+    // also work, but if we're replaying old data, then current time would be
+    // newer than the timestamps in the data, and that would cause strange time
+    // values in the sample log.
+    Kernel::DateAndTime now = timeFromPacket(pkt);
+    // addProperty() wants the time as an ISO 8601 string
+    m_buffer->mutableRun().addProperty("run_start", now.toISO8601String());
+
     m_workspaceInitialized = true;
   }