LogEmitterProvider.force_flush hangs and ultimately timeouts randomly

[overmeulen]

Describe your environment
Python 3.6.8
Opentelemetry Python 1.7.1
Opentelemetry Collector 0.38.0

Steps to reproduce
Note that this is a random behavior.
Regularly call LogEmitterProvider.force_flush while emitting logs.
We're using the BatchLogProcessor with schedule_delay_millis=200

What is the expected behavior?
No hanging

What is the actual behavior?
Hanging randomly

Additional context