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/config.py b/neutron_tempest_plugin/config.py
index 030a126..1bc9617 100644
--- a/neutron_tempest_plugin/config.py
+++ b/neutron_tempest_plugin/config.py
@@ -53,6 +53,10 @@
                     '"mtu":<MTU> - integer '
                     '"cidr"<SUBNET/MASK> - string '
                     '"provider:segmentation_id":<VLAN_ID> - integer'),
+    cfg.StrOpt('q_agent',
+               default=None,
+               choices=['None', 'linuxbridge', 'ovs', 'sriov'],
+               help='Agent used for devstack@q-agt.service'),
 
     # Option for feature to connect via SSH to VMs using an intermediate SSH
     # server