[VOL-2972] Revert added flows on failure

This commit consists of:
1) Reverts added flows on flow addition failure (e.g. one adapter
may return a failure in which case any corresponding flow that
has been successfully added to the other adapter will be removed).
The corresponding logical device flow will be removed as well.

2) Some minor refactoring in the mocks adapter

3) Some minor logging change to decrease the clutter when running
unit tests.

Change-Id: Ia63243e83516ef81152893563bef76c830bea022
diff --git a/rw_core/core/device/manager.go b/rw_core/core/device/manager.go
index 9990104..73ab456 100755
--- a/rw_core/core/device/manager.go
+++ b/rw_core/core/device/manager.go
@@ -334,7 +334,7 @@
 		return foundChildDevice, nil
 	}
 
-	logger.Warnw("child-device-not-found", log.Fields{"parentDeviceId": parentDevice.Id,
+	logger.Debugw("child-device-not-found", log.Fields{"parentDeviceId": parentDevice.Id,
 		"serialNumber": serialNumber, "onuId": onuID, "parentPortNo": parentPortNo})
 	return nil, status.Errorf(codes.NotFound, "%s", parentDeviceID)
 }