Delete the IPSec before the router is deleted
Delete the IPSec before the router is deleted

The termination of the IPSec connection process requires router's
netns presence to execute successfully, so the IPSec connection
deletion should be executed before the router is deleted,
rather than the router deletion.

Closes-Bug: #1696684

Change-Id: Ia5b3576c0a53647ee273d025f1f8893348ccc6c0

openstack/neutron-vpnaas,openstack/neutron-vpnaas