REGTEST: vtest can now enable mcli with its own flag

VTest can now enable mworker and mcli with separate flags so lets
update vtc files that need it. This also allows to revert the change
made with 1545a59c ("REGTESTS: make seamless-reload depend on 1.9
and above").
diff --git a/reg-tests/mcli/mcli_show_info.vtc b/reg-tests/mcli/mcli_show_info.vtc
index e92b786..dd6c620 100644
--- a/reg-tests/mcli/mcli_show_info.vtc
+++ b/reg-tests/mcli/mcli_show_info.vtc
@@ -8,7 +8,7 @@
 server s1 {
 } -start
 
-haproxy h1 -W -conf {
+haproxy h1 -W -S -conf {
     global
         nbproc 4
     defaults