Fix: bt2: enum-conversion warning in native_bt_component_class.i

Fix: bt2: enum-conversion warning in native_bt_component_class.i

clang warns about the following enumeration conversion.
  bt2/native_bt_wrap.c:3896:12: warning: implicit conversion from
  enumeration type 'enum bt_message_iterator_status' to different
  enumeration type 'enum bt_self_message_iterator_status'
  [-Wenum-conversion]
                  status = BT_MESSAGE_ITERATOR_STATUS_END;
                       	 ~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  bt2/native_bt_wrap.c:3898:12: warning: implicit conversion from
  enumeration type 'enum bt_message_iterator_status' to different
  enumeration type 'enum bt_self_message_iterator_status'
  [-Wenum-conversion]
                  status = BT_MESSAGE_ITERATOR_STATUS_AGAIN;
                       	 ~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  bt2/native_bt_wrap.c:3901:12: warning: implicit conversion from
  enumeration type 'enum bt_message_iterator_status' to different
  enumeration type 'enum bt_self_message_iterator_status'
  [-Wenum-conversion]
                  status = BT_MESSAGE_ITERATOR_STATUS_ERROR;
                       	 ~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  bt2/native_bt_wrap.c:4513:43: warning: implicit conversion from
  enumeration type 'enum bt_message_iterator_status' to different
  enumeration type 'bt_self_message_iterator_status' (aka 'enum
  bt_self_message_iterator_status') [-Wenum-conversion]
          bt_self_message_iterator_status status = BT_MESSAGE_ITERATOR_STATUS_OK;
                                          ~~~~~~   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  bt2/native_bt_wrap.c:4678:43: warning: implicit conversion from
  enumeration type 'enum bt_message_iterator_status' to different
  enumeration type 'bt_self_message_iterator_status' (aka 'enum
  bt_self_message_iterator_status') [-Wenum-conversion]
          bt_self_message_iterator_status status = BT_MESSAGE_ITERATOR_STATUS_OK;
                                        ~~~~~~   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Icb3bc0141cdd9f35a5a42420bb48167c12e70df0
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1183
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins