Delete entity synchronously in test method setup

Observed in Gradle test when it seems that the mutating command is
executed before deletion has taken effect.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=229585754

javatests/google/registry/tools/MutatingCommandTest.java

@@ -114,7 +114,7 @@ public class MutatingCommandTest {
 
   @Test
   public void testSuccess_create() throws Exception {
-    ofy().deleteWithoutBackup().entities(Arrays.asList(host1, host2, registrar1, registrar2));
+    ofy().deleteWithoutBackup().entities(Arrays.asList(host1, host2, registrar1, registrar2)).now();
     MutatingCommand command = new MutatingCommand() {
       @Override
       protected void init() {