Octavia deployment failing with undefined variable

Issue

During the deployment of Octavia, the Ansible task octavia-controller-config : include_tasks fails with the following error:

TASK [octavia-controller-config : include_tasks] *******************************"
, "fatal: [controller-0]: FAILED! => {"msg": "The conditional check 'private_key_content|length > 0' failed. The error was: error while evaluating conditional (
private_key_content|length > 0): 'ansible.vars.hostvars.HostVarsVars object' has no attribute 'private_key_content'\
\
The error appears to be in '/usr/share/openstack-tripleo-common/playbooks/roles/octavia-controller-config/tasks/main.yml': line 8, column 5, but may\
be elsewhere in the file depending on the exact syntax problem.\
\
The offending line appears to be:\
\
      node_hostname: \\"{{ hostname.stdout }}\\"\
  - include_tasks: certificate.yml\
    ^ here\