[ulib][mdns] Fix bad sizeof calculation in mdns-test.cpp

Change-Id: I803ddf134b5b151eb515bd723d91f9f04ed0c719
diff --git a/system/ulib/mdns/mdns-test.cpp b/system/ulib/mdns/mdns-test.cpp
index 9fef611..effb91a 100644
--- a/system/ulib/mdns/mdns-test.cpp
+++ b/system/ulib/mdns/mdns-test.cpp
@@ -24,8 +24,8 @@
         strcpy(rr.name, kRrName);
         rr.type = RR_TYPE_AAAA;
         rr.clazz = RR_CLASS_IN;
-        rr.rdata = (uint8_t*)kRdata;
-        rr.rdlength = sizeof(rr.rdata) / sizeof(uint8_t);
+        rr.rdata = const_cast<uint8_t*>(kRdata);
+        rr.rdlength = sizeof(kRdata);
         rr.ttl = 42;
         return true;
     }