See discussion here:
https://github.com/ArduPilot/ardupilot/issues/7331
we were getting some uninitialised variables. While it only showed up in
AP_SbusOut, it means we can't be sure it won't happen on other objects,
so safest to remove the approach
Thanks to assistance from Lucas, Peter and Francisco
This addresses the enhancement requested in: https://github.com/ArduPilot/ardupilot/issues/2424
It checks various PID values to check if they are zero, if they are and the corresponding rate forward feed is zero then it flags it as PreArm failure.
It has been added to the parameter check, so can be overridden if required.
Stop "latching" calibration checks - if an RC radio's calibration
changes after it passes once, these patches allow the rc calibraiton
checks to then fail.