REGTEST: Flag some slow reg tests.

All reg-tests/peers/*basic_sync*.vtc tests are slow reg reg tests.
diff --git a/reg-tests/peers/s_basic_sync_wo_stkt_backend.vtc b/reg-tests/peers/s_basic_sync_wo_stkt_backend.vtc
index f75c65c..14d7b00 100644
--- a/reg-tests/peers/s_basic_sync_wo_stkt_backend.vtc
+++ b/reg-tests/peers/s_basic_sync_wo_stkt_backend.vtc
@@ -2,6 +2,7 @@
 feature ignore_unknown_macro
 
 #REQUIRE_VERSION=2.0
+#REGTEST_TYPE=slow
 
 haproxy h1 -arg "-L A" -conf {
     defaults