Add new route.hasGateway() api

Fixes issues brought in by change to isHostRoute.  isHostRoute
was technically correct, but the callers really wanted hasNextHop
behavior.

bug:8597268
Change-Id: I360761ccfa98b2ba34642f717a78fa71ec1bae4f

services/java/com/android/server/ConnectivityService.java

@@ -1470,8 +1470,7 @@ public class ConnectivityService extends IConnectivityManager.Stub {
             loge("Error modifying route - no interface name");
             return false;
         }
-
-        if (r.isHostRoute() == false) {
+        if (r.hasGateway()) {
             RouteInfo bestRoute = RouteInfo.selectBestRoute(lp.getAllRoutes(), r.getGateway());
             if (bestRoute != null) {
                 if (bestRoute.getGateway().equals(r.getGateway())) {