Test: Rewrite ResolverTest.KeepListeningUDP am: 1e4e64d9 am: eb4c9964 am: 9c622115 am: c280aa78 am: ecd6c9a0 am: 3be49caa

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



Change-Id: Icde23af649e2c5e6300e9e9869c4232f50ffb9da
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>