Document issues with SIGPIPE for older versions of systemd

[rossmcdonald]

Per influxdata/influxdb#7040, there is a known issue with Go applications handling of the SIGPIPE signal, which, in older versions of systemd, is emitted by the journald process on restart. Currently if journald is restarted and InfluxDB, Telegraf, or Kapacitor are sending output to STDERR or STDOUT, they will get killed (and not restarted) when journald is restarted.

To combat this, users stuck on older versions of systemd should modify their unit files so that:

Restart=on-failure

Reads:

Restart=always

This will ensure the service is properly started in the event a SIGPIPE is sent to the process.