Agent connection issues

[TheTechromancer]

Agent is stuck in OFFLINE status, even though the docker container is up and no errors are displayed in the container's stdout.

We need to check the keepalive / retry backoff to make sure the agent is continously reconnecting.

There are also some strange status changes from the agent, i.e. a change from ONLINE to OFFLINE multiple times in a row, which shouldn't be possible.

FYSA @aconite33

[TheTechromancer]

On a fresh install, the agent claims to be connected, but the server is unaware of it, and scans stay "queued". After restarting the agent, things start working as expected. Not clear what is causing this.