Log downloads failing for larger files

[jaxxzer]

Investigate why. Is this a problem with APM FW or QGroundControl?
http://discuss.bluerobotics.com/t/simulating-gps-input-to-pixhawk-using-target-tracking-sonar/1187/21

[dheideman]

This problem appears to be due to packet loss, most likely from either a bad connection or signal degradation over the length of the tether.

It appears that the user sbmech17 was experiencing about 5% packet drop or less based on the maximum size of file they managed to download as mentioned in the post linked above. Increasing the maximum number of times QGC will attempt to retrieve each packet from the Pixhawk by one appears to allow log files in excess of 1 MB to be reliably downloaded even when 5% of packets are being dropped randomly. However less random problems, such as a cable coming loose for a few seconds, will still cause the process to time out.

Will be addressed in pull request from the following branch: https://github.com/bluerobotics/qgroundcontrol/tree/pr-increase-log-retries