Flask is run in debug mode

**Describe your environment** 
Flask is run in debug mode during testing

**Steps to reproduce**
See https://github.com/open-telemetry/opentelemetry-python/blob/main/tests/w3c_tracecontext_validation_server.py#L73

**What is the expected behavior?**
Do not run in debug mode to allow for more performant testing

**What is the actual behavior?**
Run in non-debug mode

