[SPARK-9649] Fix MasterSuite, third time's a charm

This particular test did not load the default configurations so
it continued to start the REST server, which causes port bind
exceptions.

core/src/test/scala/org/apache/spark/deploy/master/MasterSuite.scala

@@ -40,6 +40,7 @@ class MasterSuite extends SparkFunSuite with Matchers with Eventually with Priva
     conf.set("spark.deploy.recoveryMode", "CUSTOM")
     conf.set("spark.deploy.recoveryMode.factory",
       classOf[CustomRecoveryModeFactory].getCanonicalName)
+    conf.set("spark.master.rest.enabled", "false")
 
     val instantiationAttempts = CustomRecoveryModeFactory.instantiationAttempts