Mantis: prevent output setup from running

This is not required as we start tap_esc directly and load the mixer.

boards/atl/mantis-edu/init/rc.board_defaults

@@ -18,11 +18,17 @@ param set-default SENS_MAG_MODE 0
 
 param set-default EV_TSK_STAT_DIS 1
 
+# Use MAVLink log streaming
 set LOGGER_ARGS "-m mavlink"
 
 # Save missions RAM
 set DATAMAN_ARGS "-r"
 
+# We set the mixer and ESC manually.
+set MIXER_FILE ""
+set MIXER "skip"
+set OUTPUT_MODE "skip"
+
 # Start ESC already here, so that we have beeps.
 tap_esc start -d /dev/ttyS4 -n 4