[master] a52a1dd47 varnishtest: One more flexelint complaint

[Dridi Boukelmoune]

commit a52a1dd47e98da53ecb913c9faf2a3de26444136
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Fri May 28 15:38:52 2021 +0200

    varnishtest: One more flexelint complaint
    
    The assertion above wasn't enough apparently.

diff --git a/bin/varnishtest/vtc_tunnel.c b/bin/varnishtest/vtc_tunnel.c
index 7c579cf27..8e1f9e595 100644
--- a/bin/varnishtest/vtc_tunnel.c
+++ b/bin/varnishtest/vtc_tunnel.c
@@ -362,7 +362,7 @@ tunnel_write(struct tunnel *t, struct vtclog *vl, struct tunnel_lane *lane,
 	AZ(pthread_mutex_lock(&t->mtx));
 	if (lane->wrk_len > 0 && lane->buf_len != -1) {
 		assert(lane->buf_len >= 0);
-		assert(lane->wrk_len >= lane->buf_len);
+		assert(lane->wrk_len >= (size_t)lane->buf_len);
 		lane->wrk_len -= lane->buf_len;
 	}
 	lane->buf_len = l;