QueryServerTest fails for hostname upper case letters

QueryServerTest fails on the machine with uppercase letters in hostname:

org.junit.ComparisonFailure: 
Expected :HTTP/vitalii-UX331UN@EXAMPLE.COM
Actual   :HTTP/vitalii-ux331un@EXAMPLE.COM 

It appears kerberos does not work with hostnames with uppercase characters. The full explanation is in HADOOP-18047.

So need to use lowercase letters for hostname in this test to make them passing.