AP_Mission: removed create() method for objects

See discussion here:

  https://github.com/ArduPilot/ardupilot/issues/7331

we were getting some uninitialised variables. While it only showed up in
AP_SbusOut, it means we can't be sure it won't happen on other objects,
so safest to remove the approach

Thanks to assistance from Lucas, Peter and Francisco

libraries/AP_Mission/AP_Mission.h

@@ -280,6 +280,34 @@ public:
     FUNCTOR_TYPEDEF(mission_cmd_fn_t, bool, const Mission_Command&);
     FUNCTOR_TYPEDEF(mission_complete_fn_t, void);
 
+    // constructor
+    AP_Mission(AP_AHRS &ahrs, mission_cmd_fn_t cmd_start_fn, mission_cmd_fn_t cmd_verify_fn, mission_complete_fn_t mission_complete_fn) :
+        _ahrs(ahrs),
+        _cmd_start_fn(cmd_start_fn),
+        _cmd_verify_fn(cmd_verify_fn),
+        _mission_complete_fn(mission_complete_fn),
+        _prev_nav_cmd_id(AP_MISSION_CMD_ID_NONE),
+        _prev_nav_cmd_index(AP_MISSION_CMD_INDEX_NONE),
+        _prev_nav_cmd_wp_index(AP_MISSION_CMD_INDEX_NONE),
+        _last_change_time_ms(0)
+    {
+        // load parameter defaults
+        AP_Param::setup_object_defaults(this, var_info);
+
+        // clear commands
+        _nav_cmd.index = AP_MISSION_CMD_INDEX_NONE;
+        _do_cmd.index = AP_MISSION_CMD_INDEX_NONE;
+
+        // initialise other internal variables
+        _flags.state = MISSION_STOPPED;
+        _flags.nav_cmd_loaded = false;
+        _flags.do_cmd_loaded = false;
+    }
+
+    /* Do not allow copies */
+    AP_Mission(const AP_Mission &other) = delete;
+    AP_Mission &operator=(const AP_Mission&) = delete;    
+    
     // mission state enumeration
     enum mission_state {
         MISSION_STOPPED=0,
@@ -287,19 +315,6 @@ public:
         MISSION_COMPLETE=2
     };
 
-    static AP_Mission create(AP_AHRS &ahrs,
-                             mission_cmd_fn_t cmd_start_fn,
-                             mission_cmd_fn_t cmd_verify_fn,
-                             mission_complete_fn_t mission_complete_fn) {
-        return AP_Mission(ahrs, cmd_start_fn, cmd_verify_fn, mission_complete_fn);
-    }
-
-    constexpr AP_Mission(AP_Mission &&other) = default;
-
-    /* Do not allow copies */
-    AP_Mission(const AP_Mission &other) = delete;
-    AP_Mission &operator=(const AP_Mission&) = delete;
-
     ///
     /// public mission methods
     ///
@@ -458,30 +473,6 @@ private:
         uint8_t do_cmd_all_done : 1; // true if all "do"/"conditional" commands have been completed (stops unnecessary searching through eeprom for do commands)
     } _flags;
 
-    AP_Mission(AP_AHRS &ahrs, mission_cmd_fn_t cmd_start_fn, mission_cmd_fn_t cmd_verify_fn, mission_complete_fn_t mission_complete_fn) :
-        _ahrs(ahrs),
-        _cmd_start_fn(cmd_start_fn),
-        _cmd_verify_fn(cmd_verify_fn),
-        _mission_complete_fn(mission_complete_fn),
-        _prev_nav_cmd_id(AP_MISSION_CMD_ID_NONE),
-        _prev_nav_cmd_index(AP_MISSION_CMD_INDEX_NONE),
-        _prev_nav_cmd_wp_index(AP_MISSION_CMD_INDEX_NONE),
-        _last_change_time_ms(0)
-    {
-        // load parameter defaults
-        AP_Param::setup_object_defaults(this, var_info);
-
-        // clear commands
-        _nav_cmd.index = AP_MISSION_CMD_INDEX_NONE;
-        _do_cmd.index = AP_MISSION_CMD_INDEX_NONE;
-
-        // initialise other internal variables
-        _flags.state = MISSION_STOPPED;
-        _flags.nav_cmd_loaded = false;
-        _flags.do_cmd_loaded = false;
-    }
-
-
     ///
     /// private methods
     ///

libraries/AP_Mission/examples/AP_Mission_test/AP_Mission_test.cpp

@@ -14,11 +14,11 @@ public:
     void loop();
 
 private:
-    AP_InertialSensor ins = AP_InertialSensor::create();
-    AP_Baro baro = AP_Baro::create();
-    AP_GPS  gps = AP_GPS::create();
-    Compass compass = Compass::create();
-    AP_AHRS_DCM ahrs = AP_AHRS_DCM::create(ins, baro, gps);
+    AP_InertialSensor ins;
+    AP_Baro baro;
+    AP_GPS  gps;
+    Compass compass;
+    AP_AHRS_DCM ahrs{ins, baro, gps};
 
     // global constants that control how many verify calls must be made for a command before it completes
     uint8_t verify_nav_cmd_iterations_to_complete = 3;
@@ -44,10 +44,10 @@ private:
     void run_replace_cmd_test();
     void run_max_cmd_test();
 
-    AP_Mission mission = AP_Mission::create(ahrs,
+    AP_Mission mission{ahrs,
             FUNCTOR_BIND_MEMBER(&MissionTest::start_cmd, bool, const AP_Mission::Mission_Command &),
             FUNCTOR_BIND_MEMBER(&MissionTest::verify_cmd, bool, const AP_Mission::Mission_Command &),
-            FUNCTOR_BIND_MEMBER(&MissionTest::mission_complete, void));
+            FUNCTOR_BIND_MEMBER(&MissionTest::mission_complete, void)};
 };
 
 static MissionTest missiontest;