Tripleo quickstart failing on convert-image task with error: 'overcloud_image' is undefined

Description: Tripleo quickstart failing on convert-image task with error: 'overcloud_image' is undefined

After merge of https://review.opendev.org/c/openstack/tripleo-quickstart/+/801703

On baremetal env ci/ manual tripleo deployments, We are hitting below error:-

~~~
2021-09-15 23:15:11.527717 | primary | TASK [convert-image : check if we have an {{ overcloud_image }}.qcow2 to start from] ***
2021-09-15 23:15:11.527728 | primary | Wednesday 15 September 2021 23:15:11 -0400 (0:00:02.724) 1:59:27.474 ***
2021-09-15 23:15:11.558197 | primary | fatal: [baremetal-env]: FAILED! => {}
2021-09-15 23:15:11.558249 | primary |
2021-09-15 23:15:11.558259 | primary | MSG:
2021-09-15 23:15:11.558278 | primary |
2021-09-15 23:15:11.558287 | primary | The task includes an option with an undefined variable. The error was: 'overcloud_image' is undefined
2021-09-15 23:15:11.558295 | primary |
2021-09-15 23:15:11.558304 | primary | The error appears to be in '/home/zuul/src/opendev.org/openstack/tripleo-quickstart/roles/convert-image/tasks/main.yml': line 7, column 3, but may
2021-09-15 23:15:11.558313 | primary | be elsewhere in the file depending on the exact syntax problem.
2021-09-15 23:15:11.558322 | primary |
2021-09-15 23:15:11.558330 | primary | The offending line appears to be:
2021-09-15 23:15:11.558339 | primary |
2021-09-15 23:15:11.558347 | primary |
2021-09-15 23:15:11.558355 | primary | - name: check if we have an {{ overcloud_image }}.qcow2 to start from
2021-09-15 23:15:11.558369 | primary | ^ here
2021-09-15 23:15:11.558378 | primary | We could be wrong, but this one looks like it might be an issue with
2021-09-15 23:15:11.558386 | primary | missing quotes. Always quote template expression brackets when they
2021-09-15 23:15:11.558394 | primary | start a value. For instance:
2021-09-15 23:15:11.558402 | primary |
2021-09-15 23:15:11.558411 | primary | with_items:
2021-09-15 23:15:11.558419 | primary | - {{ foo }}
2021-09-15 23:15:11.558427 | primary |
2021-09-15 23:15:11.558436 | primary | Should be written as:
2021-09-15 23:15:11.558444 | primary |
2021-09-15 23:15:11.558452 | primary | with_items:
2021-09-15 23:15:11.558461 | primary | - "{{ foo }}"
2021-09-15 23:15:11.558469 | primary |
2021-09-15 23:15:11.559612 | primary |
2021-09-15 23:15:11.559639 | primary | PLAY RECAP *********************************************************************
2021-09-15 23:15:11.559647 | primary | localhost : ok=11 changed=5 unreachable=0 failed=0 skipped=28 rescued=0 ignored=0
2021-09-15 23:15:11.559652 | primary | baremetal-env : ok=137 changed=55 unreachable=0 failed=1 skipped=93 rescued=0 ignored=15
~~~

Possible solutions:-

1) Add extras-common as a dep

`overcloud_image: overcloud-full` is defined in tqe extras-common role.

https://opendev.org/openstack/tripleo-quickstart-extras/src/branch/master/roles/extras-common/defaults/main.yml#L170

Add extras-common as a dep, as that will pull required var and that role doesn't execute any task.

Cons: This will add a dependency on quickstart-extras roles.

2) Add `overcloud_image: overcloud-full` var to "common" role defaults

Pros: This will avoid dep on quickstart-extras roles, so quickstart roles can be used independently of quickstart-extras