Description of problem:

While trying OVS to OVN migration[1] (ovn_migration.sh setup-mtu-t1) after upgrading from osp13 to 16.1 we noticed ansible file[2] still trying to fetch and restart the container using docker command.

~~~
(undercloud) [stack@undercloud-0 ovn_migration]$  ovn_migration.sh setup-mtu-t1                                                                                                                                    
ansible-playbook 2.9.10
  config file = /home/stack/ovn_migration/ansible.cfg
  configured module search path = ['/home/stack/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python3.6/site-packages/ansible
  executable location = /usr/bin/ansible-playbook
  python version = 3.6.8 (default, Dec  5 2019, 15:45:45) [GCC 8.3.1 20191121 (Red Hat 8.3.1-5)]
Using /home/stack/ovn_migration/ansible.cfg as config file
[WARNING]: Invalid characters were found in group names but not replaced, use -vvvv to see details

PLAYBOOK: reduce-dhcp-renewal-time.yml ****************************************************************************************************************************************************************************
1 plays in /home/stack/ovn_migration/playbooks/reduce-dhcp-renewal-time.yml

PLAY [overcloud-controllers] **************************************************************************************************************************************************************************************

TASK [Gathering Facts] ********************************************************************************************************************************************************************************************
task path: /home/stack/ovn_migration/playbooks/reduce-dhcp-renewal-time.yml:3
Monday 13 July 2020  14:55:17 +0000 (0:00:00.120)       0:00:00.120 *********** 
.
.
.
.
TASK [Restart neutron dhcp agent] *********************************************************************************************************************************************************************************
task path: /home/stack/ovn_migration/playbooks/reduce-dhcp-renewal-time.yml:22
Monday 13 July 2020  14:55:30 +0000 (0:00:00.570)       0:00:12.364 *********** 
fatal: [controller-0]: FAILED! => {"changed": false, "cmd": "docker restart", "msg": "[Errno 2] No such file or directory: b'docker': b'docker'", "rc": 2}
...ignoring
META: ran handlers
META: ran handlers

PLAY RECAP ********************************************************************************************************************************************************************************************************
controller-0               : ok=4    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=1   
~~~

~~~
~~~
(undercloud) [stack@undercloud-0 ovn_migration]$ cat /home/stack/ovn_migration/playbooks/reduce-dhcp-renewal-time.yml                
---

- hosts: overcloud-controllers
  tasks:
  - name: Update dhcp_agent configuration file option 'dhcp_renewal_time'
    ini_file:
      path=/var/lib/config-data/puppet-generated/neutron/etc/neutron/dhcp_agent.ini
      section=DEFAULT
      backup=yes
      option=dhcp_renewal_time
      value={{ renewal_time }}
      create=no
    ignore_errors: yes

  - block:
    - name: Get the neutron dhcp agent docker id
      shell:
        docker ps | grep neutron_dhcp | awk '{print $1}'   <<<<<<< docker instead of podman
      register: dhcp_agent_docker_id
      ignore_errors: yes

    - name: Restart neutron dhcp agent
      command: docker restart {{ dhcp_agent_docker_id.stdout }}     <<<<<<< docker instead of podman
      ignore_errors: yes
~~~


[1] https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/16.1-beta/html-single/networking_with_open_virtual_network/index#about-ml2-ovs-to-ovn-migration  
[2] /home/stack/ovn_migration/playbooks/reduce-dhcp-renewal-time.yml



Version-Release number of selected component (if applicable):
OSP 16.1