Clear out status logs from air side when drone restarts

[steveatinfincia]

The air unit in OpenHD will send messages over the microservice channel that allows the ground side and QOpenHD to know when the drone has connected or rebooted.

When that happens, QOpenHD requests all status messages from the status service running on the air side. As a result there will be a flood of new status messages arriving, but it will look like they are duplicates unless we clear the old ones out first.

We should remove the messages received from the air side right before requesting the new ones.

[steveatinfincia]

Alternatively we could either keep air/ground messages separate in tabs, or put a marker in the log/display showing that a drone connected or rebooted and that the messages after that point are new.