v.io: use test.V23Init instead of v23.Init in test code

test.V23Init creates a context that's suitable for tests, including a
test blessing and no prod mounttable root. Using test.V23Init everywhere
in tests gives us a choke-point for adding test-specific configuration
of the runtime and context.

Change-Id: I078a614e49a4f185afa4d6c25bb3c1d5b880cd1e
diff --git a/go/src/v.io/x/js.core/test_service/test_serviced/main.go b/go/src/v.io/x/js.core/test_service/test_serviced/main.go
index 7dab405..4bd6d21 100644
--- a/go/src/v.io/x/js.core/test_service/test_serviced/main.go
+++ b/go/src/v.io/x/js.core/test_service/test_serviced/main.go
@@ -13,11 +13,12 @@
 	"v.io/x/ref/lib/flags"
 	"v.io/x/ref/lib/signals"
 	_ "v.io/x/ref/runtime/factories/generic"
+	"v.io/x/ref/test"
 )
 
 func main() {
 	flags.SetDefaultHostPort("127.0.0.1:0")
-	ctx, shutdown := v23.Init()
+	ctx, shutdown := test.V23Init()
 	defer shutdown()
 
 	ctx, s, err := v23.WithNewDispatchingServer(ctx, "test_service", NewDispatcher())