Migrate DnsUtilsTest to the NetworkMonitor version of FakeDns. am: 9cef6de3bd

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/3261832

Change-Id: I46e91464abc8fe92c54043acb7263df48605e2cc
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>