ZOOKEEPER-4340: add tab unit test for StringUtils#split

Adding a test case to StringUtils to ensure spaces expressed as something other than ' ' are covered.

Author: Aditya Patruni <adityapatruni@Adityas-MBP.home>

Reviewers: maoling <maoling@apache.org>

Closes #1732 from apatruni/apatruni/tests and squashes the following commits:

0b25e6865 [Aditya Patruni] add space after , on line 43
dc700a9b0 [Aditya Patruni] Fix formatting
8e686d859 [Aditya Patruni] add tab test

zookeeper-server/src/test/java/org/apache/zookeeper/test/StringUtilTest.java

@@ -38,6 +38,9 @@ public class StringUtilTest extends ZKTestCase {
 
         final String s3 = "1, , 2";
         assertEquals(Arrays.asList("1", "2"), StringUtils.split(s3, ","));
+
+        final String s4 = "1, \t , 2";
+        assertEquals(Arrays.asList("1", "2"), StringUtils.split(s4, ","));
     }
 
     @Test