Fix bug 1216: Remove machines only for native charms

Updates revision of Python libjuju to 2.8.4

Change-Id: I3f41eead305349eba5d404f5f3d61d33f0536aca
Signed-off-by: David Garcia <david.garcia@canonical.com>
diff --git a/n2vc/tests/unit/utils.py b/n2vc/tests/unit/utils.py
index ee4dd96..d960c70 100644
--- a/n2vc/tests/unit/utils.py
+++ b/n2vc/tests/unit/utils.py
@@ -56,6 +56,18 @@
     dns_name = "FAKE ENDPOINT"
     model_name = "FAKE MODEL"
     entity_type = "machine"
+    safe_data = {"instance-id": "myid"}
+
+    async def destroy(self, force):
+        pass
+
+
+class FakeManualMachine(MagicMock):
+    entity_id = "2"
+    dns_name = "FAKE ENDPOINT"
+    model_name = "FAKE MODEL"
+    entity_type = "machine"
+    safe_data = {"instance-id": "manual:myid"}
 
     async def destroy(self, force):
         pass