Enforce checkstyle for unit test codes

- First time contributer is likely to start with unit-test code,
  so it is probably better to enforce the ONOS code style for
  unit test codes also.

Change-Id: Id665e55b0f0bee7232dfb18ce6a7f9ea8cc3b164
diff --git a/pom.xml b/pom.xml
index 9a32fb3..80dbf31 100644
--- a/pom.xml
+++ b/pom.xml
@@ -59,6 +59,7 @@
           <propertiesLocation>${basedir}/conf/checkstyle/checkstyle_maven.properties</propertiesLocation>
           <failsOnError>false</failsOnError>
           <logViolationsToConsole>true</logViolationsToConsole>
+          <includeTestSourceDirectory>true</includeTestSourceDirectory>
         </configuration>
         <executions>
           <execution>
@@ -428,6 +429,7 @@
               (under build and reporting)
           -->
           <propertiesLocation>${basedir}/conf/checkstyle/checkstyle_maven.properties</propertiesLocation>
+          <includeTestSourceDirectory>true</includeTestSourceDirectory>
         </configuration>
         <reportSets>
           <reportSet>