ecore con dns - a failed dns lookup is not an err log event

spewing out errors for a failed dns lookup is not somehting to ERR out
in logs all the time. it is at best a debug log. the caller handles
the failed connect itself.

@fix

src/lib/ecore_con/ecore_con_dns.c

@@ -96,7 +96,7 @@ _ecore_con_dns_check(Ecore_Con_DNS *dns)
         return 1;
 
       default:
-        ERR("resolve failed: %s", dns_strerror(error));
+        DBG("resolve failed: %s", dns_strerror(error));
         goto error;
      }