Merge "Move jni file descriptor helper code to libnetjniutils" am: 47e51e4b19 am: e606b556c5

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/1519501

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I046443bc65419d4bb589cb99f0713a3dc38e1a9b