[6.0] 10ced1f29 Check the backend connection failures get counted

[Dridi Boukelmoune]

commit 10ced1f29c3c71cec951b757d4d87bf01a5289a8
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Thu Jun 14 13:53:15 2018 +0000

    Check the backend connection failures get counted

diff --git a/bin/varnishtest/tests/b00015.vtc b/bin/varnishtest/tests/b00015.vtc
index cc6df6d22..5f3b69c03 100644
--- a/bin/varnishtest/tests/b00015.vtc
+++ b/bin/varnishtest/tests/b00015.vtc
@@ -92,3 +92,6 @@ client c1 {
 } -run
 
 delay .1
+
+varnish v1 -expect VBE.vcl1.foo.fail_econnrefused > 0
+varnish v1 -expect VBE.vcl1.foo.helddown > 0