Do not use RABBITMQ_LOGS to configure logging

[lukebakken]

TL;DR a configuration file should be used instead in /etc/rabbitmq/conf.d to set defaults.

Full discussion here:

rabbitmq/rabbitmq-server#4303

cc @gerhard @mkuratczyk in case one of you remembers why RABBITMQ_LOGS=- was chosen. Thanks!

[tianon]

I believe it was chosen because it pre-dates the ini-style configuration file format. 😅

[lukebakken]

Thanks. I'll open a PR with our suggested changes.