[4.1] 5ec70b3 Mention the witness facility in varnishtest(1)

[Dridi Boukelmoune]

commit 5ec70b34f39a2d682b2b16ac0b2f7f5a29faa071
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Fri Jul 10 18:04:19 2015 +0200

    Mention the witness facility in varnishtest(1)

diff --git a/doc/sphinx/reference/varnishtest.rst b/doc/sphinx/reference/varnishtest.rst
index f75a621..14c4ee4 100644
--- a/doc/sphinx/reference/varnishtest.rst
+++ b/doc/sphinx/reference/varnishtest.rst
@@ -50,6 +50,8 @@ The following options are available:
 
 -v               Verbose mode: always report test log
 
+-W               Enable the witness facility for locking
+
 -h               Show help
 
 file             File to use as a script