fix 1183: Delete native charms before destroying juju model

Destroying the juju model automatically destroys all applications and machines.
However it is not deleted if they are native charms in pending status.

Change-Id: I8b3580e201f1d403d36b6e07fa3947ea4a655683
Signed-off-by: tierno <alfonso.tiernosepulveda@telefonica.com>
diff --git a/osm_lcm/ns.py b/osm_lcm/ns.py
index 9267b45..4bed2c6 100644
--- a/osm_lcm/ns.py
+++ b/osm_lcm/ns.py
@@ -3225,8 +3225,9 @@
                 vca_type = vca.get("type")
                 exec_terminate_primitives = (not operation_params.get("skip_terminate_primitives") and
                                              vca.get("needed_terminate"))
-                # For helm we must destroy_ee
-                destroy_ee = "True" if vca_type == "helm" else "False"
+                # For helm we must destroy_ee. Also for native_charm, as juju_model cannot be deleted if there are
+                # pending native charms
+                destroy_ee = "True" if vca_type in ("helm", "native_charm") else "False"
                 task = asyncio.ensure_future(
                     self.destroy_N2VC(logging_text, db_nslcmop, vca, config_descriptor, vca_index,
                                       destroy_ee, exec_terminate_primitives))