Enable advanced log routing when running Logagent with Docker

[adnanrahic]

One killer feature we should consider is to enable log routing to different locations and indices while also using the whitelisting feature.

Todo:

• [x] Enable starting the Logagent without using a LOGS_TOKEN in the Logagent container env if LOGS_ENABLED_DEFAULT=false
• [x] Enable reading LOGS_ENABLED=true and both LOGS_TOKEN and LOGS_RECEIVER_URL from the whitelisted container's env
• [x] Pinpoint bugs/issues with the current implementation that seems to work only with different LOGS_TOKENs but not different LOGS_RECEIVER_URLs
• [x] Explore option to use logagent.conf file in this setup

Keeping this issue open as a reminder to tackle this ASAP.

[adnanrahic]

Start by looking here: https://github.com/sematext/logagent-js/blob/master/lib/plugins/input/docker/dockerInspect.js