Test cases for Drill-6104: Added Logfile Reader

[Charles Givre]

Hello all, 
I submitted this PR for a logfile parser for Drill 
(https://github.com/apache/drill/pull/1114 
<https://github.com/apache/drill/pull/1114>) .  I need to write unit tests for 
it, however I really have no idea how to do so.  Could someone point me to an 
example or something so that the PR will pass the CI tests?
TIA,
- C