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_tls_basic_sync_wo_stkt_backend.vtc b/reg-tests/peers/s_tls_basic_sync_wo_stkt_backend.vtc
index f3d556d..6a28eb1 100644
--- a/reg-tests/peers/s_tls_basic_sync_wo_stkt_backend.vtc
+++ b/reg-tests/peers/s_tls_basic_sync_wo_stkt_backend.vtc
@@ -3,6 +3,7 @@
 
 #REQUIRE_VERSION=2.0
 #REQUIRE_OPTIONS=OPENSSL
+#REGTEST_TYPE=slow
 
 haproxy h1 -arg "-L A" -conf {
     defaults