Fix up a little test failure.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1494792 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/ipc/TestSaslRPC.java

@@ -91,6 +91,9 @@ public class TestSaslRPC {
   public void setup() {
     conf = new Configuration();
     conf.set(HADOOP_SECURITY_AUTHENTICATION, "kerberos");
+    conf.setBoolean(
+        CommonConfigurationKeys.IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY,
+        true);
     UserGroupInformation.setConfiguration(conf);
   }