[VOL-2454] Fix for device deletion in the rw_core

When a parent device is deleted, its child devices are deleted
as well.  The state machine in the Core ensures this process occurs.
However, there were "duplicate" codes during the parent device
deletion where it was triggering child devices in being deleted
again.  This is incorrect is being addressed by this change.

Change-Id: I8dbbe48e97f70638a0ea28444825452b366da137
diff --git a/rw_core/core/device_agent.go b/rw_core/core/device_agent.go
index 8cbc63a..d71da27 100755
--- a/rw_core/core/device_agent.go
+++ b/rw_core/core/device_agent.go
@@ -150,7 +150,8 @@
 func (agent *DeviceAgent) stop(ctx context.Context) {
 	defer agent.lockDevice.Unlock()
-	log.Debug("stopping-device-agent")
+	log.Debugw("stopping-device-agent", log.Fields{"deviceId": agent.deviceID, "parentId": agent.parentID})
 	// First unregister any callbacks
 	agent.deviceProxy.UnregisterCallback(model.POST_UPDATE, agent.processUpdate)
@@ -165,8 +166,7 @@
 		log.Debugw("device-already-removed", log.Fields{"id": agent.deviceID})
 	agent.exitChannel <- 1
-	log.Debug("device-agent-stopped")
+	log.Debugw("device-agent-stopped", log.Fields{"deviceId": agent.deviceID, "parentId": agent.parentID})
 // Load the most recent state from the KVStore for the device.