nova.py: Set defaults for OpenStack settings

- auth_system
- region_name

These are config settings that could be left out in many scenarios, but
the current code is requiring them. With this in place, I can get by
with this minimal .ini file:

```ini
[openstack]
version=1.1
auth_url=http://{keystone_host}:5000/v2.0
project_id=web
username={username}
api_key={password}
```
Change variable from pattern to name to correctly indicate what is being passed to the callback.
Reset play attribute on callback plugins when a play fails.
Remove runner_on_error callback that is never used.
Change parameter from pattern to name for playbook_on_play_start in example callback plugins.
Return service name, display name, start mode and state from win_service module.
Add integration tests for win_service module.
Fix for #7368 breaks peering connections. Unreak them.
ansible_ec2_instance-id key incorrect

ansible_ec2_instance-id should be ansible_ec2_instance_id

fatal: [*IP*] => One or more undefined variables: 'dict object' has no attribute 'ansible_ec2_instance-id'
removed port from domain name qualification, fixes 7941
Data from inventory scripts should be able to use nested Jinja2 expressions.
Remove validation of RDS DB instance type names because Amazon frequently adds new ones
Merge pull request #8015 from cchurch/test_win_service

win_service module updates and tests
Merge pull request #8012 from cchurch/callback_cleanup

Callback plugin cleanup
Fix missing msg argument

The following patch adds a missing 'msg=' syntax. An exception is raised
in ansible if this block is reached during the execution of the module

    TypeError: fail_json() takes exactly 1 argument (2 given)

With the 'msg=' added, you get a more informative error. For example

    msg: No settings provided to update_domain().
Allow empty yaml vars files

Fixes #7843
Merge pull request #8024 from kcghost/7941

removed port from domain name qualification, fixes #7941
Merge pull request #8022 from psa/vpc-gateway-peering

Fix for #7368 breaks peering connections. Unreak them.
Merge pull request #8023 from btashton/patch-1

ansible_ec2_instance-id key incorrect
Merge pull request #8036 from sqs/remove-fragile-RDS-instance-type-validation

Remove validation of RDS DB instance type names because Amazon frequently adds new ones