Fix just some nodes osp (#1039)

* Fixes to just-some-nodes-example for OSP

- sample_vars_osp.yml
- support both instance.image and instance.image_id in default heat template
- support volumes[].name and volumes[].volume_name

* Add security group to the nodes

* Add CHANGEME comments

* key_name is not mandatory in OSP, add a default

fix this error:

TASK [infra-common-ssh-config-generate : Add bastion proxy config to workdir ssh config file] *************************************************************************************************
Thursday 23 January 2020  16:56:01 +0000 (0:00:00.178)       0:01:45.182 ******
fatal: [localhost]: FAILED! => {"msg": "The task includes an option with an undefined variable. The error was: 'key_name' is undefined\n\nThe error appears to be in '/ansible/roles/infra-common-ssh-config-generate/tasks/main.yml': line 36, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: Add bastion proxy config to workdir ssh config file\n  ^ here\n"}

* add changeme comment