ZOOKEEPER-4325: Fix bug when list "/" with ZkUtil::listSubTreeBFS

[autumind]

Fix bug ZOOKEEPER-4325

[maoling]

@autumind
You really have an empty line at the end of the file: ZKUtil.java. After you revert it, I will merge it asap at this weekend(07-11).

git  diff 70f70d821c2

@@ -290,4 +291,4 @@ public static String aclToString(List<ACL> acls) {
         }
         return sb.toString();
     }
-}
\ No newline at end of file
+}
diff --git a/zookeeper-server/src/test/java/org/apache/zookeeper/ZKUtilTest.java b/zookeeper-server/src/test/java/org/apache/zookeeper/ZKUtilTest.java
index 1111c2a23..3ad1ed94f 100644

[autumind]

@autumind
You really have an empty line at the end of the file: ZKUtil.java. After you revert it, I will merge it asap at this weekend(07-11).

git  diff 70f70d821c2

@@ -290,4 +291,4 @@ public static String aclToString(List<ACL> acls) {
         }
         return sb.toString();
     }
-}
\ No newline at end of file
+}
diff --git a/zookeeper-server/src/test/java/org/apache/zookeeper/ZKUtilTest.java b/zookeeper-server/src/test/java/org/apache/zookeeper/ZKUtilTest.java
index 1111c2a23..3ad1ed94f 100644

What a silly mistake, I've reverted it.

[maoling]

@autumind You had reverted the empty line at the end of the file: ZKUtil.java ???

[autumind]

@autumind You had reverted the empty line at the end of the file: ZKUtil.java ???

Actually, I removed the empty line, but I have no idea why this commit
Remove empty line at the end of the file has no diffs in github view. Besides, ZKUtil.java comes one more line cause I added a line of comment in my patch.

[maoling]

@autumind

• What IDE do you use? It must be not the problem of Github.
• vim doesn't work, please use other tool like sublime, IDEA, or VS code
• Important things are to be repeated for 3 times:
  use git diff (git diff 70f70d8) to observe the changes before you submit.
  use git diff (git diff 70f70d8) to observe the changes before you submit.
  use git diff (git diff 70f70d8) to observe the changes before you submit.