Description of problem:
OSP15 deployment with 1 controller + 1compute

TASK [Debug output for task: Start containers for step 4] ***************************************************************************************************************************************************************
ok: [controller-0] => {
    "failed_when_result": false,
    "outputs.stdout_lines | default([]) | union(outputs.stderr_lines | default([]))": [
        "stdout: ",
        "stderr: "
    ]
}
ok: [compute-0] => {
    "failed_when_result": false,
    "outputs.stdout_lines | default([]) | union(outputs.stderr_lines | default([]))": []
}

TASK [Clean container_puppet_tasks for {{ansible_hostname}} step {{step}}] **********************************************************************************************************************************************
ok: [controller-0]
ok: [compute-0]

TASK [Calculate container_puppet_tasks for {{ansible_hostname}} step {{step}}] ******************************************************************************************************************************************
fatal: [controller-0]: FAILED! => {"msg": "The conditional check 'vars[item.service_name + '_short_bootstrap_node_name'] == ansible_hostname' failed. The error was: error while evaluating conditional (vars[item.service_name + '_short_bootstrap_node_name'] == ansible_hostname): 'ansible_hostname' is undefined\n\nThe error appears to be in '/home/stack/config-download/common_deploy_steps_tasks.yaml': line 529, column 7, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n    - name: Calculate container_puppet_tasks for {{ansible_hostname}} step {{step}}\n      ^ here\nWe could be wrong, but this one looks like it might be an issue with\nmissing quotes. Always quote template expression brackets when they\nstart a value. For instance:\n\n    with_items:\n      - {{ foo }}\n\nShould be written as:\n\n    with_items:\n      - \"{{ foo }}\"\n"}


[stack@undercloud-0 ~]$ cat overcloud_deploy.sh 
#!/bin/bash

openstack overcloud deploy \
--timeout 100 \
--templates /usr/share/openstack-tripleo-heat-templates \
--stack overcloud \
--libvirt-type kvm \
--ntp-server clock1.rdu2.redhat.com \
-e /home/stack/virt/config_lvm.yaml \
-e /usr/share/openstack-tripleo-heat-templates/environments/network-isolation.yaml \
-e /home/stack/virt/network/network-environment.yaml \
-e /home/stack/virt/network/dvr-override.yaml \
-e /home/stack/virt/enable-tls.yaml \
-e /home/stack/virt/inject-trust-anchor.yaml \
-e /home/stack/virt/public_vip.yaml \
-e /usr/share/openstack-tripleo-heat-templates/environments/ssl/tls-endpoints-public-ip.yaml \
-e /home/stack/virt/hostnames.yml \
-e /home/stack/virt/nodes_data.yaml \
-e ~/containers-prepare-parameter.yaml \
-e /home/stack/virt/extra_templates.yaml \
--stack-only

openstack overcloud config download   --name overcloud   --config-dir ~/config-download
cd config-download/
tripleo-ansible-inventory   --ansible_ssh_user heat-admin   --static-yaml-inventory inventory.yaml


inject fail to stop execution after last task with tag - step3

run manual installation 
ansible-playbook   -i inventory.yaml   --private-key ~/.ssh/id_rsa   --become   ~/config-download/deploy_steps_playbook.yaml


inject task before first task with tag - step4

- hosts: localhost
  name: test_skip
  gather_facts: yes
  any_errors_fatal: yes
  tasks:
    - name: test
      ping: 


ansible-playbook   -i inventory.yaml   --private-key ~/.ssh/id_rsa --start-at-task="test"   --become   ~/config-download/deploy_steps_playbook.yaml

Version-Release number of selected component (if applicable):
openstack-tripleo-heat-templates-10.5.1-0.20190701110422.889d4d4.el8ost.noarch
ansible-2.8.1-1.e
RHOS_TRUNK-15.0-RHEL-8-20190701.n.0l8ae.noarch

How reproducible:
always

Steps to Reproduce:
1.Deploy with --stack-only
2. Introduce fail to stop oc deployment with config-download after step3
3. Try to deploy with --start-at-task

Actual results:
TASK [Debug output for task: Start containers for step 4] ***************************************************************************************************************************************************************
ok: [controller-0] => {
    "failed_when_result": false,
    "outputs.stdout_lines | default([]) | union(outputs.stderr_lines | default([]))": [
        "stdout: ",
        "stderr: "
    ]
}
ok: [compute-0] => {
    "failed_when_result": false,
    "outputs.stdout_lines | default([]) | union(outputs.stderr_lines | default([]))": []
}

TASK [Clean container_puppet_tasks for {{ansible_hostname}} step {{step}}] **********************************************************************************************************************************************
ok: [controller-0]
ok: [compute-0]

TASK [Calculate container_puppet_tasks for {{ansible_hostname}} step {{step}}] ******************************************************************************************************************************************
fatal: [controller-0]: FAILED! => {"msg": "The conditional check 'vars[item.service_name + '_short_bootstrap_node_name'] == ansible_hostname' failed. The error was: error while evaluating conditional (vars[item.service_name + '_short_bootstrap_node_name'] == ansible_hostname): 'ansible_hostname' is undefined\n\nThe error appears to be in '/home/stack/config-download/common_deploy_steps_tasks.yaml': line 529, column 7, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n    - name: Calculate container_puppet_tasks for {{ansible_hostname}} step {{step}}\n      ^ here\nWe could be wrong, but this one looks like it might be an issue with\nmissing quotes. Always quote template expression brackets when they\nstart a value. For instance:\n\n    with_items:\n      - {{ foo }}\n\nShould be written as:\n\n    with_items:\n      - \"{{ foo }}\"\n"}


Expected results:
passed

Additional info: