Skip exception if model doesn't exist after delete failure

- bug: 2017
Change-Id: I9d118602c747840a4a32fd670c8724c82c1ee094
Signed-off-by: David Garcia <david.garcia@canonical.com>
(cherry picked from commit 5c96662b238a20ecc7c516269a0b051e3b0333eb)
diff --git a/n2vc/libjuju.py b/n2vc/libjuju.py
index 028cea8..f32ea09 100644
--- a/n2vc/libjuju.py
+++ b/n2vc/libjuju.py
@@ -1223,6 +1223,10 @@
                 controller,
                 timeout=total_timeout,
             )
+        except Exception as e:
+            if not await self.model_exists(model_name, controller=controller):
+                return
+            raise e
         finally:
             if model:
                 await self.disconnect_model(model)