Replace useTls with mode in PrivateDnsConfig am: 707915c012 am: 017a0bf0ba

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/2841436

Change-Id: I5a9a27f638092ff971fce6b215ca53a3e42d4e43
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>