Disable px4 logging for running larger swarms

[tfoote]

About half the load from the px4 module is coming from the logging. I made this change locally and was able to fly 10 vehicles on my laptop which previously maxed out at about 5.

The above change is not flexible enough to submit upstream as it is not configurable. But it's something we should consider doing when deploying larger swarms The individual flight logs are not as important unless you want to debug the autopilot specifically.