Remove an interface before more invasive changes

Remove NetworkTimeUpdateService interface, replace it with its only
implementation.

Test: build only
Change-Id: Idf607957b7abe9a27f4fec2ebe3c0ee9e74f1694

services/java/com/android/server/SystemServer.java

@@ -1695,7 +1695,7 @@ public final class SystemServer {
             if (!isWatch && !disableNetworkTime) {
                 traceBeginAndSlog("StartNetworkTimeUpdateService");
                 try {
-                    networkTimeUpdater = new NetworkTimeUpdateServiceImpl(context);
+                    networkTimeUpdater = new NetworkTimeUpdateService(context);
                     ServiceManager.addService("network_time_update_service", networkTimeUpdater);
                 } catch (Throwable e) {
                     reportWtf("starting NetworkTimeUpdate service", e);