Ensure motors are stopped before a reboot. Ensure hard fault handler

doesn't use potentially unitialised data to update the motors.  Pause
for 50ms before rebooting after updating disabling the motors to ensure
the timer hardware and ESCs havea chance to react.

This commit might help with #123

src/main/io/serial_cli.c

@@ -1344,6 +1344,7 @@ static void cliRateProfile(char *cmdline)
 static void cliReboot(void) {
     cliPrint("\r\nRebooting");
     waitForSerialPortToFinishTransmitting(cliPort);
+    stopMotors();
     systemReset();
 }