Test: Rewrite ResolverTest.KeepListeningUDP am: 1e4e64d9 am: 1be21de1 am: 034e1bf3 am: 14cade6b

Original change: https://android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/2466320



Change-Id: Ie987d66051491b551cbc02931675a6fdb2a5677c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>