BUG/MINOR: systemd: ExecStartPre must use -Ws

This line should disappear in a future version but we should still fix
ExecStartPre with -Ws like we've done in 9def142.

It's a complementary fix that must be backported with 9def142
("BUG/MINOR: systemd: must check the configuration using -Ws").

(cherry picked from commit 6f58c13797dc02a5b0c5be943f6d5396e486bd71)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/admin/systemd/haproxy.service.in b/admin/systemd/haproxy.service.in
index cb7bbda..49d3c52 100644
--- a/admin/systemd/haproxy.service.in
+++ b/admin/systemd/haproxy.service.in
@@ -7,7 +7,7 @@
 EnvironmentFile=-/etc/default/haproxy
 EnvironmentFile=-/etc/sysconfig/haproxy
 Environment="CONFIG=/etc/haproxy/haproxy.cfg" "PIDFILE=/run/haproxy.pid" "EXTRAOPTS=-S /run/haproxy-master.sock"
-ExecStartPre=@SBINDIR@/haproxy -f $CONFIG -c -q $EXTRAOPTS
+ExecStartPre=@SBINDIR@/haproxy -Ws -f $CONFIG -c -q $EXTRAOPTS
 ExecStart=@SBINDIR@/haproxy -Ws -f $CONFIG -p $PIDFILE $EXTRAOPTS
 ExecReload=@SBINDIR@/haproxy -Ws -f $CONFIG -c -q $EXTRAOPTS
 ExecReload=/bin/kill -USR2 $MAINPID