After ml2/ovs to ml2/networking-ovn migration neutron resources are left on the database

Description of problem:
After ovn migration completed I check the output of OpenStack network agent list
and it looks like we can see the legacy neutron agent. They are not alive but still, I expected that they will not display in OVN deployment after migration process performed.

Ansible [migration: Deleting the neutron agents] actually ran in the controller-0. it is expected to be run in localhost (i.e undercloud)

TASK [migration : Generate neutron resources cleanup script] **********************************************************************************************************************************
task path: /home/stack/ovn_migration/playbooks/roles/migration/tasks/delete-neutron-resources.yml:12
Monday 19 November 2018 11:17:31 -0500 (0:00:00.586) 1:06:27.269 *******
META: noop
META: noop
META: noop
META: noop
changed: [controller-0] => {"changed": true, "checksum": "fd0d852ef79dfbe3c5384eecce8fec53579acf6c", "dest": "/home/stack/ovn_migration/delete_neutron_resources/delete-neutron-resources.sh", "gid": 0, "group": "root", "md5sum": "9f41d4008b512c54b2ffbf84a1b8cb4f", "mode": "0744", "owner": "root", "secontext": "unconfined_u:object_r:user_home_t:s0", "size": 551, "src": "/home/heat-admin/.ansible/tmp/ansible-tmp-1542644251.88-161854948129152/source", "state": "file", "uid": 0}

TASK [migration : Deleting the neutron agents] ************************************************************************************************************************************************
task path: /home/stack/ovn_migration/playbooks/roles/migration/tasks/delete-neutron-resources.yml:18
Monday 19 November 2018 11:17:32 -0500 (0:00:01.061) 1:06:28.330 *******
META: noop
META: noop
META: noop
META: noop
changed: [controller-0] => {"changed": true, "cmd": "/home/stack/ovn_migration/delete_neutron_resources/delete-neutron-resources.sh 2>&1 > /home/stack/ovn_migration/delete_neutron_resources/delete-neutron-resources.sh.log", "delta": "0:00:01.479081", "end": "2018-11-19 16:17:34.880606", "rc": 0, "start": "2018-11-19 16:17:33.401525", "stderr": "", "stderr_lines": [], "stdout": "+ source /home/stack/overcloudrc\n/home/stack/ovn_migration/delete_neutron_resources/delete-neutron-resources.sh: line 5: /home/stack/overcloudrc: No such file or directory\n++ openstack network agent list\n++ awk '{print $2}'\n++ grep neutron-\nMissing value auth-url required for auth plugin password\n++ openstack network list\n++ awk '{print $2}'\n++ grep 'HA network tenant'\nMissing value auth-url required for auth plugin password\n+ exit 0", "stdout_lines": ["+ source /home/stack/overcloudrc", "/home/stack/ovn_migration/delete_neutron_resources/delete-neutron-resources.sh: line 5: /home/stack/overcloudrc: No such file or directory", "++ openstack network agent list", "++ awk '{print $2}'", "++ grep neutron-", "Missing value auth-url required for auth plugin password", "++ openstack network list", "++ awk '{print $2}'", "++ grep 'HA network tenant'", "Missing value auth-url required for auth plugin password", "+ exit 0"]}
META: ran handlers
META: ran handlers