AP_Motors: fixed motor knocking issue on tilt quadplanes

[tridge]

the motor output was happening twice per loop with different values for tilt quadplanes using motor matrix

not tested yet

[IamPete1]

We do output PWM twice, but its after a cork and before a push, so I don't understand how its getting out to the motors.

[IamPete1]

I have added the same fix for the tri-copter backend.

[IamPete1]

Apparently this does fix, but I still don't understand the cork push thing.

[IamPete1]

To be clear, I don't think we should merge this without understanding it. I also think there may be is a issue with how motor_enabled_mask is set, because we do the normal output first then the throttle override it must be 0 on the first call. We should test the tailsitter case too which is the other user of the motor_enabled_mask stuff.

[tridge]

@IamPete1 I think this is a better fix:
#29521

[tridge]

went with cork/push fix