test1247: use http server to get the port number set

Follow-up to 0f5db7b263f
diff --git a/tests/data/test1247 b/tests/data/test1247
index 48c5ccd..ff127eb 100644
--- a/tests/data/test1247
+++ b/tests/data/test1247
@@ -17,7 +17,7 @@
 # Client-side
 <client>
 <server>
-none
+http
 </server>
  <name>
 --fail-early