Turn purge_dups on by default

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4239 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/mgt_param.c

@@ -751,7 +751,7 @@ static const struct parspec input_parspec[] = {
 	{ "purge_dups", tweak_bool, &master.purge_dups, 0, 0,
 		"Detect and eliminate duplicate purges.\n",
 		0,
-		"off", "bool" },
+		"on", "bool" },
 	{ "cli_banner", tweak_bool, &master.cli_banner, 0, 0,
 		"Emit CLI banner on connect.\n"
 		"Set to off for compatibility with pre 2.1 versions.\n",