Automatically remove sensors after agent shutdown.

tools.descartes.prisma.agent.wildfly/src/main/java/tools/descartes/prisma/agent/wildfly/service/ModelExtractionService.java

@@ -73,6 +73,7 @@ import tools.descartes.prisma.core.impl.CDOModelRepository;
 import tools.descartes.prisma.core.impl.RabbitMQMessageBus;
 import tools.descartes.prisma.core.util.ModelSkeletonUtil;
 import tools.descartes.prisma.model.sensor.ComponentSensor;
+import tools.descartes.prisma.model.sensor.Sensor;
 import tools.descartes.prisma.model.sensor.SensorFactory;
 import tools.descartes.prisma.model.skeleton.ModelSkeleton;
 import tools.descartes.prisma.model.skeleton.SkeletonFactory;
@@ -181,6 +182,11 @@ public class ModelExtractionService extends AgentController implements Service<M
 					// shut down
 					return true;
 				}
+				if (object instanceof Sensor<?>) {
+					// Sensor are not available anymore after the agent shuts
+					// down.
+					return true;
+				}
 				if (object instanceof AssemblyContext || object instanceof AssemblyConnector
 						|| object instanceof ProvidingDelegationConnector
 						|| object instanceof RequiringDelegationConnector || object instanceof InterfaceProvidingRole