Copter: althold remove redundant z-axis init

ArduCopter/mode_althold.cpp

@@ -8,10 +8,6 @@
 // althold_init - initialise althold controller
 bool Copter::ModeAltHold::init(bool ignore_checks)
 {
-    // initialize vertical speeds and leash lengths
-    pos_control->set_speed_z(-get_pilot_speed_dn(), g.pilot_speed_up);
-    pos_control->set_accel_z(g.pilot_accel_z);
-
     // initialise position and desired velocity
     if (!pos_control->is_active_z()) {
         pos_control->set_alt_target_to_current_alt();