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/src/test/java/net/onrc/onos/apps/sdnip/PrefixTest.java b/src/test/java/net/onrc/onos/apps/sdnip/PrefixTest.java
index a000564..cee6898 100644
--- a/src/test/java/net/onrc/onos/apps/sdnip/PrefixTest.java
+++ b/src/test/java/net/onrc/onos/apps/sdnip/PrefixTest.java
@@ -65,11 +65,12 @@
         assertEquals(p1.hashCode(), p3.hashCode());
     }
 
+    private static final int MAX_PREFIX_LENGTH = 32;
+
     @Test
     public void testPrefixReturnsSame() {
         //Create a prefix of all 1s for each prefix length.
         //Check that Prefix doesn't mangle it
-        final int MAX_PREFIX_LENGTH = 32;
         for (int prefixLength = 1; prefixLength <= MAX_PREFIX_LENGTH; prefixLength++) {
             byte[] address = new byte[MAX_PREFIX_LENGTH / Byte.SIZE];