Move tests to use TestDataHelper for reading resources

TestDataHelper is build exactly to prevent direct reads of resources. It caches
the resources and makes sure they are in the correct directory.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=191785004

javatests/google/registry/tools/UpdatePremiumListCommandTest.java

@@ -15,7 +15,7 @@
 package google.registry.tools;
 
 import static google.registry.request.JsonResponse.JSON_SAFETY_PREFIX;
-import static google.registry.util.ResourceUtils.readResourceUtf8;
+import static google.registry.testing.TestDataHelper.loadFile;
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyMapOf;
 import static org.mockito.Matchers.eq;
@@ -44,11 +44,10 @@ public class UpdatePremiumListCommandTest<C extends UpdatePremiumListCommand>
   public void init() throws Exception {
     command.setConnection(connection);
     servletPath = "/_dr/admin/updatePremiumList";
-    premiumTermsPath = writeToNamedTmpFile(
-        "example_premium_terms.csv",
-        readResourceUtf8(
-            UpdatePremiumListCommandTest.class,
-            "testdata/example_premium_terms.csv"));
+    premiumTermsPath =
+        writeToNamedTmpFile(
+            "example_premium_terms.csv",
+            loadFile(UpdatePremiumListCommandTest.class, "example_premium_terms.csv"));
     when(connection.send(
         eq(UpdatePremiumListAction.PATH),
         anyMapOf(String.class, String.class),