Fix zuul javascript cookie load

The default filter value for the status page was not being set correctly.
As such the filter would incorrectly remove all results. When no cookie
is set, make sure the filter is blank.

Change-Id: I4868db8b357373d1fd94dc6ffc7528692b75dd8d
diff --git a/etc/status/public_html/jquery.zuul.js b/etc/status/public_html/jquery.zuul.js
index 01f8bd3..3085b26 100644
--- a/etc/status/public_html/jquery.zuul.js
+++ b/etc/status/public_html/jquery.zuul.js
@@ -50,7 +50,7 @@
         }, options);
 
         var collapsed_exceptions = [];
-        var current_filter = read_cookie('zuul_filter_string', current_filter);
+        var current_filter = read_cookie('zuul_filter_string', '');
         var $jq;
 
         var xhr,