[5.1] d87dcf1 This assert will not hold in all error situations.

[Poul-Henning Kamp]

commit d87dcf17d367c3db62c7ee56f61c57b45dce8fc8
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Mon Mar 20 08:41:03 2017 +0000

    This assert will not hold in all error situations.

diff --git a/bin/varnishtest/vtc_http2.c b/bin/varnishtest/vtc_http2.c
index b472d81..bef8689 100644
--- a/bin/varnishtest/vtc_http2.c
+++ b/bin/varnishtest/vtc_http2.c
@@ -836,7 +836,7 @@ receive_frame(void *priv)
 		continue;
 	}
 	AZ(pthread_mutex_unlock(&hp->mtx));
-	AZ(vsb);
+	assert(vtc_error || vsb == NULL);
 	return (NULL);
 }