Copter: fixed upgrade of parameters

now that we dynamically allocate many key objects in copter we need to
move the parameter upgrade code to after when the objects are allocated

ArduCopter/Parameters.cpp

@@ -1075,8 +1075,6 @@ void Copter::load_parameters(void)
     // setup AP_Param frame type flags
     AP_Param::set_frame_type_flags(AP_PARAM_FRAME_COPTER);
     
-    // upgrade parameters
-    convert_pid_parameters();
 }
 
 // handle conversion of PID gains from Copter-3.3 to Copter-3.4

ArduCopter/system.cpp

@@ -651,4 +651,7 @@ void Copter::allocate_motors(void)
         }
 #endif
     }
+
+    // upgrade parameters. This must be done after allocating the objects
+    convert_pid_parameters();
 }