Added a wipe-out command; we need to revisit how to either make the devices come back or the links not come back.
diff --git a/core/trivial/src/main/java/org/onlab/onos/net/trivial/device/impl/SimpleDeviceStore.java b/core/trivial/src/main/java/org/onlab/onos/net/trivial/device/impl/SimpleDeviceStore.java
index 6317b14..ece82e1 100644
--- a/core/trivial/src/main/java/org/onlab/onos/net/trivial/device/impl/SimpleDeviceStore.java
+++ b/core/trivial/src/main/java/org/onlab/onos/net/trivial/device/impl/SimpleDeviceStore.java
@@ -139,8 +139,7 @@
     DeviceEvent markOffline(DeviceId deviceId) {
         synchronized (this) {
             Device device = devices.get(deviceId);
-            checkArgument(device != null, DEVICE_NOT_FOUND, deviceId);
-            boolean removed = availableDevices.remove(deviceId);
+            boolean removed = device != null && availableDevices.remove(deviceId);
             return !removed ? null :
                     new DeviceEvent(DEVICE_AVAILABILITY_CHANGED, device, null);
         }