Common Telegraf configuration is parsed twice

Description

Telegraf has two options for specifying configuration files paths:

• --config - for a single configuration file
• --config-directory - for multiple configuration files

We use the second option and set it to /etc/telegraf. Unfortunately, it seems that --config is still set by default to /etc/telegraf/telegraf.conf, so that file gets parsed TWICË.

This results in duplicated InfluxDB output.