Zero initialize ExifMnoteData<vendor> during construction with exif_mnote_data_<vendor>_new. am: c9da78d8d9 am: 31c126f5ac am: 444375e5d8 am: afc6c77748

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/libexif/+/16248754

Change-Id: Ib4a5e61af013811df9b32c3182ecf0dfd5b8a5c5