[master] 6ddb405ff varnishtest: Constify barrier_sock_sync()

[Dridi Boukelmoune]

commit 6ddb405ffbcc3418efce20425f7c9cd92dd40b87
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Thu Jun 24 10:24:27 2021 +0200

    varnishtest: Constify barrier_sock_sync()
    
    Spotted by flexelint.

diff --git a/bin/varnishtest/vtc_barrier.c b/bin/varnishtest/vtc_barrier.c
index 5c8ea2590..98df1fc8a 100644
--- a/bin/varnishtest/vtc_barrier.c
+++ b/bin/varnishtest/vtc_barrier.c
@@ -336,7 +336,7 @@ barrier_cond_sync(struct barrier *b, struct vtclog *vl)
 }
 
 static void
-barrier_sock_sync(struct barrier *b, struct vtclog *vl)
+barrier_sock_sync(const struct barrier *b, struct vtclog *vl)
 {
 	struct vsb *vsb;
 	const char *err;