Remove systemd output redirection

[jsternberg]

Let systemd handle the output so the journal can be used. This also
let's the user configure if the journal stores the output of this
service to a file instead of setting the location.

Fixes #6824.

[jsternberg]

@rossmcdonald is this a reasonable change so that systemd log files are managed by systemd? It might need to be documented since the log file won't be in the same location as the fallback init script.

[rossmcdonald]

I believe we'll need to keep the -config /etc/influxdb/influxdb.conf, unless it's being set in the INFLUXD_OPTS environment variable. I have no issues with removing the redirects, though. I never understood why we had the redirects in the first place.

[jsternberg]

The configuration file is in a default location that gets read automatically as of 0.13 so the argument isn't needed anymore. It might still be good to put it in though to make it explicit. I'll re-add it.

[rossmcdonald]

👍 Looks great, thanks!

[jsternberg]

@jwilder should this be merged for 1.0 or should this be delayed until 1.1?

[jwilder]

Does this mean that systems using systemD will no longer have logs in /var/log/influxdb by default now? If so, need to add that to the release notes.

[jsternberg]

Yes. If we merge this, systemd will use whatever is the default for the system (typically journald -u influxdb.service).

[jwilder]

Ok. Please add details to release notes. Otherewise, 👍