Lock the sms counters properly

Fixes: #768



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@5210 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/storage_synth.c

@@ -120,6 +120,8 @@ SMS_Finish(struct object *obj)
 	sto->len = vsb_len(vsb);
 	sto->space = vsb_len(vsb);
 	obj->len = sto->len;
+	Lck_Lock(&sms_mtx);
 	VSC_main->sms_nbytes += sto->len;
 	VSC_main->sms_balloc += sto->len;
+	Lck_Unlock(&sms_mtx);
 }