Copter: fixed collective input with H_SV_MAN=1 for heli

when H_SV_MAN=1 we do direct pass-thru so the user can test swash
range. The problem is that it uses norm_input() for throttle, which
depends on RC3_TRIM. Nowhere else in heli or copter do we depend on
RC3_TRIM, so the user gets a misleading idea of behaviour when testing
their swash.

ArduCopter/radio.cpp

@@ -182,5 +182,8 @@ void Copter::set_throttle_zero_flag(int16_t throttle_control)
 // pass pilot's inputs to motors library (used to allow wiggling servos while disarmed on heli, single, coax copters)
 void Copter::radio_passthrough_to_motors()
 {
-    motors->set_radio_passthrough(channel_roll->norm_input(), channel_pitch->norm_input(), channel_throttle->norm_input(), channel_yaw->norm_input());
+    motors->set_radio_passthrough(channel_roll->norm_input(),
+                                  channel_pitch->norm_input(),
+                                  channel_throttle->get_control_in_zero_dz()*0.001,
+                                  channel_yaw->norm_input());
 }