Add scenario test for trunk E2E flow

Add Scenario test "test_parent_port_connectivity_after_trunk_deleted"
to verify the E2E flow of fix proposed for Bug: #1794424
"Enable delete bound trunk for linux bridge agent"

Co-Authored-By: Allain Legacy <Allain.legacy@windriver.com>

Depends-On: https://review.openstack.org/#/c/605589/
Change-Id: Ic2e02f4b5dc8d7930e251340d8be194733b0a4f7
Related-Bug: #1794424
Story: 2003889
diff --git a/neutron_tempest_plugin/api/base.py b/neutron_tempest_plugin/api/base.py
index 028d901..e1eafcd 100644
--- a/neutron_tempest_plugin/api/base.py
+++ b/neutron_tempest_plugin/api/base.py
@@ -764,7 +764,7 @@
         return trunk
 
     @classmethod
-    def delete_trunk(cls, trunk, client=None):
+    def delete_trunk(cls, trunk, client=None, detach_parent_port=True):
         """Delete network trunk
 
         :param trunk: dictionary containing trunk ID (trunk['id'])
@@ -790,7 +790,7 @@
             parent_port.update(client.show_port(parent_port['id'])['port'])
             return not parent_port['device_id']
 
-        if not is_parent_port_detached():
+        if detach_parent_port and not is_parent_port_detached():
             # this could probably happen when trunk is deleted and parent port
             # has been assigned to a VM that is still running. Here we are
             # assuming that device_id points to such VM.