Fixed race-conditions in null providers.

Change-Id: Ie1acd9d74e1277776a5981d21043671010b37343

@@ -382,7 +382,9 @@ public class DeviceManager
                                                      port.portSpeed())));
             store.updatePorts(this.provider().id(), deviceId, descs);
             try {
-                post(store.markOffline(deviceId));
+                if (mastershipService.getLocalRole(deviceId) == MASTER) {
+                    post(store.markOffline(deviceId));
+                }
             } catch (IllegalStateException e) {
                 log.warn("Failed to mark {} offline", deviceId);
                 // only the MASTER should be marking off-line in normal cases,

@@ -339,7 +339,6 @@ public class NullProviders {
             packetProvider.stop();
             flowRuleProvider.stop();
             delay(500);
-            rejectMastership();
             simulator.tearDownTopology();
             simulator = null;
         }
@@ -396,7 +395,8 @@ public class NullProviders {
 
         @Override
         public boolean isReachable(DeviceId deviceId) {
-            return topoShape.equals("configured") || deviceService.isAvailable(deviceId);
+            return topoShape.equals("configured") ||
+                    (simulator != null && simulator.contains(deviceId));
         }
 
         @Override

@@ -182,9 +182,9 @@ public abstract class TopologySimulator {
                 new DefaultDeviceDescription(id.uri(), Device.Type.SWITCH,
                                              "ON.Lab", "0.1", "0.1", "1234",
                                              new ChassisId(i));
+        deviceIds.add(id);
         deviceProviderService.deviceConnected(id, desc);
         deviceProviderService.updatePorts(id, buildPorts(hostCount + infrastructurePorts));
-        deviceIds.add(id);
     }
 
 //    /**
@@ -287,10 +287,10 @@ public abstract class TopologySimulator {
      * Removes any devices previously advertised by this provider.
      */
     protected void removeDevices() {
-        prepareForDeviceEvents(deviceService.getDeviceCount());
-        deviceService.getDevices()
-                .forEach(device -> deviceService.removeDevice(device.id()));
+        prepareForDeviceEvents(deviceIds.size());
+        deviceIds.forEach(deviceProviderService::deviceDisconnected);
         waitForDeviceEvents();
+        deviceIds.clear();
     }
 
 
@@ -358,6 +358,16 @@ public abstract class TopologySimulator {
         return ports;
     }
 
+    /**
+     * Indicates whether or not the simulation knows of this device.
+     *
+     * @param deviceId device identifier
+     * @return true if device is known
+     */
+    public boolean contains(DeviceId deviceId) {
+        return deviceIds.contains(deviceId);
+    }
+
     // Counts down number of device added/available/removed events.
     private class DeviceEventCounter implements DeviceListener {
         @Override