Increase code coverage in DnsStats

To increase the code coverage in DnsStats, DnsStats unit test
should also cover DnsStats::dump().

Test: resolv_unit_test passed
Change-Id: I5eae976a2b6ce87cc2e5f66ae66facf3f2df4caa
diff --git a/DnsStats.h b/DnsStats.h
index 526f468..40dad94 100644
--- a/DnsStats.h
+++ b/DnsStats.h
@@ -106,10 +106,10 @@
     // TODO: Compatible support for getResolverInfo().
     // TODO: Support getSortedServers().
 
+    static constexpr size_t kLogSize = 128;
+
   private:
     std::map<Protocol, ServerStatsMap> mStats;
-
-    static constexpr size_t kLogSize = 128;
 };
 
 }  // namespace android::net