update keylist to use bool and stdint value for key not found. (#572)

* Updated keylist to use bool and stdint value for key not found.

* Added Keylist_Index_Key to deprecate Keylist_Key function

* Changed the deprecated Keylist_Key API to Keylist_Index_Key

* Added unit test for Keylist_Index_Key API

src/bacnet/basic/object/lo.c

@@ -174,7 +174,11 @@ unsigned Lighting_Output_Count(void)
  */
 uint32_t Lighting_Output_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**