vm: 'shutdown' method for network interfaces

Instead of 'delete_host' parameter for 'destroy'.

circle/vm/models/instance.py

@@ -945,7 +945,7 @@ class Instance(AclBase, VirtualMachineDescModel, TimeStampedModel):
             # Destroy networks
             with act.sub_activity('destroying_net'):
                 for net in self.interface_set.all():
-                    net.destroy(delete_host=False)
+                    net.shutdown()
 
             # Suspend vm
             with act.sub_activity('suspending'):
@@ -1075,7 +1075,7 @@ class Instance(AclBase, VirtualMachineDescModel, TimeStampedModel):
             # Destroy networks
             with act.sub_activity('destroying_net'):
                 for net in self.interface_set.all():
-                    net.destroy(delete_host=False)
+                    net.shutdown()
 
             with act.sub_activity('migrate_vm'):
                 queue_name = self.get_remote_queue_name('vm')

circle/vm/models/network.py

@@ -142,11 +142,14 @@ class Interface(Model):
             args=[self.get_vmnetwork_desc()],
             queue=self.instance.get_remote_queue_name('net'))
 
-    def destroy(self, delete_host=True, user=None, task_uuid=None):
+    def shutdown(self, user=None, task_uuid=None):
         net_tasks.destroy.apply_async(
             args=[self.get_vmnetwork_desc()],
             queue=self.instance.get_remote_queue_name('net'))
-        if delete_host and self.host is not None:
+
+    def destroy(self, user=None, task_uuid=None):
+        self.shutdown(user, task_uuid)
+        if self.host is not None:
             self.host.delete()
 
     def save_as_template(self, instance_template):