Resolve compile error caused by ReturnValueIgnored

Author: terence-yoo

hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestRowCacheCanCacheRow.java

@@ -210,7 +210,7 @@ private static void testWith(Function<Get, Get> func) {
     Assert.assertTrue(RowCacheService.canCacheRow(get, region));
 
     // expect false
-    func.apply(get);
+    Get unused = func.apply(get);
     Assert.assertFalse(RowCacheService.canCacheRow(get, region));
   }
 }