Stop registering native mdns service

NsdService switched from Netd native solution to Java solution on
Android U. MDNS service provided by Netd will be removed from Android V.

1. Stop registering native mdns service from V.
2. Stop startDaemon() in NsdManager from V.
3. As a double safety, return early in NsdService methods that call the
   native mdns service when platform version is V+.
4. Modify NsdManagerTest to cover V+ behavior.

Bug: 298594687
Test: Build. Presubmit.
Change-Id: Ifdac8f7a44aa57d93d453ba482ec473a2b531452