Also check actual duty when applying custom speed setting

Bug Fix

What does this MR do?

This MR will, after a short delay due to duty change latency, check the actual reported duty when determining if it should apply a new duty setting for a custom speed setting (fan curve).

This will help issues where other programs are also trying to control the device. (coolero won't give up basically)

Related issues

Relates to #64 (closed)

Checklist

• Application works as expected when running from source
• AppImage build compiles and runs successfully
• Flatpak build compiles and runs successfully
• There are dependency changes
• Performance considerations have been taken into account
• This MR is ready to be merged