Description of problem:

When Octavia is enabled, "openstack overcloud run --nodes controller-0" fails with showing the following error.
~~~
TASK [remove TLS proxy if configured and running] ******************************
Thursday 25 July 2019  03:07:54 -0400 (0:00:00.117)       0:02:14.697 ********* 
fatal: [controller-0]: FAILED! => {"msg": "The conditional check 'internal_tls_enabled|bool' failed. The error was: error while evaluating conditional (internal_tls_enabled|bool): 'internal_tls_enabled' is undefined\n\nThe error appears to have been in '/var/lib/mistral/17b1432a-b7c8-4967-b33c-f4c1a738ee6e/Controller/update_tasks.yaml': line 171, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n  when: step|int == 5\n- docker:\n  ^ here\n"}
~~~

Version-Release number of selected component (if applicable):
RHOSP13z7

How reproducible:
Always

Steps to Reproduce:
1. Try minor update procedure according to the production doc[1]

[1] https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/13/html/keeping_red_hat_openstack_platform_updated/index

Actual results:
openstack overcloud run --nodes Controller fails

Expected results:
openstack overcloud run --nodes Controller succeeds without any errors


Additional info:

I'm afraid that this is the degradation caused by wisgifying octavia api
 https://github.com/openstack/tripleo-heat-templates/commit/450d50f544f601b9d3f6aea13b70802bec272573