--[BUGFIX] Background renderer should not create extra contexts

[jturner65]

Motivation and Context

This PR fixes an issue where an additional GL context was being created in the Background Renderer, which was causing problems, including seg faults with examples/tutorials/async_rendering.py

How Has This Been Tested

Existing C++ and python tests pass

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[0mdc]

Is the code from examples/tutorials/async_rendering.py tested somewhere?

[0mdc]

LGTM!

[jturner65]

Is the code from examples/tutorials/async_rendering.py tested somewhere?

Yes, it is part of the python tests. test_example.py