drivers output on debug level does not include requests

[bzz]

For debugging driver issues, it's very convenient to be able to see per-request logs in the debug output.

But right now

docker run --rm -it -p 9432:9432 bblfsh/python-driver:v2.8.1 --log-level=debug
bblfshd-cli <something>

would only result in logs

[2019-03-19T13:11:43Z]  INFO cpp-driver version: v1.2.0 (build: 2019-02-22T17:32:28Z)
[2019-03-19T13:11:43Z] DEBUG executing native binary ...
[2019-03-19T13:11:43Z]  INFO server listening in 0.0.0.0:9432 (tcp)

while the same using bblfshd would produce detailed entry for every grpc request.