Change the publicity of the variable

Author: KodaiD

integration-test/src/main/java/com/scalar/db/api/DistributedStorageAdminPermissionIntegrationTestBase.java

@@ -45,7 +45,7 @@ public abstract class DistributedStorageAdminPermissionIntegrationTestBase {
           .addSecondaryIndex(COL_NAME4)
           .build();
 
-  protected DistributedStorageAdmin adminForRootUser;
+  private DistributedStorageAdmin adminForRootUser;
   private DistributedStorageAdmin adminForNormalUser;
   private String normalUserName;
   private String normalUserPassword;