Merge "Reset mNetDataPrefixes when Thread goes down." into main am: e71571d178

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3094998

Change-Id: Iae41b5c9440a2b413af48a6f6922c3c4a25153f9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>