[core] Driver log file lost after multiple `ray.init`s in the same process

[stephanie-wang]

What is the problem?

Ray version and other system information (Python version, TensorFlow version, OS): 0.9dev

The driver logs to a python-core-driver-* file correctly during the first ray.init(), but then a subsequent ray.shutdown() and ray.init() does not produce a second file in the session logs. This is probably only relevant for pytests that run multiple ray sessions in the same process.

Reproduction (REQUIRED)

Any checked in pytest. For example, pytest python/ray/tests/test_basic.py.

• I have verified my script runs in a clean environment and reproduces the issue.
• I have verified the issue also occurs with the latest wheels.

[stephanie-wang]

Introduced in #9230.