This removes fluentd in favor of using fluentbit, which is lighter (in
memory usage) and seems to be more actively maintained.
Fluentbit's config file format is different from fluentd's. It also
doesn't support the same record modification stuff that fluentd
supports, so we have to change the influxdb query slightly. This
means that after an upgrade, the new CLI may won't work for querying older
logs. Hopefully, this slight breakage is acceptable; if users
really need older logs they can use the older CLI.
