LIQCTLD: handle WARN and ERROR log levels appropriately

Bug Fix

What does this MR do?

This adds proper handling for WARN and ERROR logging levels in the liqctld service.

Related issues

Fixes #214 (closed)

Checklist

• Application works as expected when running from source
• There are dependency changes
• Liquidctl device mock tests are successful (if applicable)
• Any needed documentation changes have been made
• This MR is ready to be merged