Put the path to client_secrets in a config option.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=148214513

javatests/google/registry/config/RegistryConfigTest.java

@@ -0,0 +1,35 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.config;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class RegistryConfigTest {
+
+  public RegistryConfigTest() {}
+
+  @Test
+  public void test_clientSecretFilename() {
+    RegistryConfigSettings config = YamlUtils.getConfigSettings();
+    // Verify that we're pulling this from the default.
+    assertThat(RegistryConfig.getClientSecretFilename()).isEqualTo(
+        "/google/registry/tools/resources/client_secret.json");
+  }
+}