Copter: override do_aux_function_armdisarm method to set armed_with_switch

As well as removing the code duplication, this only sets the flag if
arming was actually successful.  armed-with-switch is used when setting
various state, and it isn't entirely clear that we only use it when
armed.  This would seem to be a safer option.

ArduCopter/RC_Channel.cpp

@@ -142,6 +142,16 @@ void RC_Channel_Copter::do_aux_function_change_mode(const Mode::Number mode,
     }
 }
 
+void RC_Channel_Copter::do_aux_function_armdisarm(const aux_switch_pos_t ch_flag)
+{
+    RC_Channel::do_aux_function_armdisarm(ch_flag);
+    if (copter.arming.is_armed()) {
+        // remember that we are using an arming switch, for use by
+        // set_throttle_zero_flag
+        copter.ap.armed_with_switch = true;
+    }
+}
+
 // do_aux_function - implement the function invoked by auxiliary switches
 void RC_Channel_Copter::do_aux_function(const aux_func_t ch_option, const aux_switch_pos_t ch_flag)
 {
@@ -380,23 +390,6 @@ void RC_Channel_Copter::do_aux_function(const aux_func_t ch_option, const aux_sw
 #endif
             break;
 
-        case AUX_FUNC::ARMDISARM:
-            // arm or disarm the vehicle
-            switch (ch_flag) {
-            case HIGH:
-                copter.arming.arm(AP_Arming::Method::AUXSWITCH);
-                // remember that we are using an arming switch, for use by set_throttle_zero_flag
-                copter.ap.armed_with_switch = true;
-                break;
-            case MIDDLE:
-                // nothing
-                break;
-            case LOW:
-                copter.arming.disarm();
-                break;
-            }
-            break;
-
         case AUX_FUNC::SMART_RTL:
 #if MODE_SMARTRTL_ENABLED == ENABLED
             do_aux_function_change_mode(Mode::Number::SMART_RTL, ch_flag);

ArduCopter/RC_Channel.h

@@ -15,6 +15,7 @@ protected:
 
 private:
 
+    void do_aux_function_armdisarm(const aux_switch_pos_t ch_flag) override;
     void do_aux_function_change_mode(const Mode::Number mode,
                                      const aux_switch_pos_t ch_flag);