MAJOR: systemd-wrapper: get rid of the wrapper

The master worker mode obsoletes the systemd-wrapper, to ensure that
nobody uses it anymore, the code has been removed.
diff --git a/contrib/systemd/haproxy.service.in b/contrib/systemd/haproxy.service.in
index ca38d70..81b4951 100644
--- a/contrib/systemd/haproxy.service.in
+++ b/contrib/systemd/haproxy.service.in
@@ -7,7 +7,7 @@
 # socket if you want seamless reloads.
 Environment="CONFIG=/etc/haproxy/haproxy.cfg" "PIDFILE=/run/haproxy.pid"
 ExecStartPre=@SBINDIR@/haproxy -f $CONFIG -c -q
-ExecStart=@SBINDIR@/haproxy-systemd-wrapper -f $CONFIG -p $PIDFILE
+ExecStart=@SBINDIR@/haproxy -W -f $CONFIG -p $PIDFILE
 ExecReload=@SBINDIR@/haproxy -f $CONFIG -c -q
 ExecReload=/bin/kill -USR2 $MAINPID
 KillMode=mixed