Switch service check in the testing for the `no_settings` scenario

[mcdonnnj]

💡 Summary

We should uncomment the test logic to use the service.exists attribute when possible. We should remove the test that is currently in-place as a workaround when doing so.

Motivation and context

Currently a workaround is used to determine whether or not a service exists due to pytest-dev/pytest-testinfra#757. If pytest-dev/pytest-testinfra#754 is merged and a new release containing it is cut we can switch to using this more straightforward check.

Implementation notes

When uncommenting the code we should also remove the existing test as it will be superfluous.

[jsf9k]

@mcdonnnj - See pytest-dev/pytest-testinfra#767, which was released in version 10.1.1.