Fix exposing private messages files through attachments with a content URI. am: 0d5452146c am: f5c73b1923 am: 83d5883687 am: 5b110f95e9 am: ff1c734aeb

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Messaging/+/23089831

Change-Id: I163a39ab25cd6c67467c0b11cf8049d591dadd8c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>