[TX Calibration]: Shuts off all actuator output during calibration. This
prevented a dangerous situation where until the TX channels were calibrated
the actuators would respond to transmitter jitter.

Fixes #579.
[TX Calibration]: Fixed missing break statement as well as
forcing ActuatorCommand to update at the standard slow rate.
Merge pull request #937 from kubark42/fix-spastic-actuators-during-calibration

Shuts off all actuator output during calibration.