Merge "Expose MIN_MTU_V6 as a public, @hide constant" am: 4833cf6910 am: 919265831e am: 0b417d78e9

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1505072

Change-Id: I0b91313fdf767e66200b61d74f7d59f5128411d2