remove test instances even when failing to remove the snap

The tests may fail to remove the snap for various reasons. In order
to avoid leaking harness instances that could potentially
exhaust the host resources, we'll clean the harness instances even if
we were unable to remove the snap.

tests/integration/tests/conftest.py

@@ -192,9 +192,10 @@ def instances(
             LOG.debug("Generating inspection reports for test instances")
             _generate_inspection_report(h, instance.id)
 
-        util.remove_k8s_snap(instance)
-
-        h.delete_instance(instance.id)
+        try:
+            util.remove_k8s_snap(instance)
+        finally:
+            h.delete_instance(instance.id)
 
 
 @pytest.fixture(scope="function")