Downstream Caches - PURGE request has a double slash

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What steps will reproduce the problem?
1. Configure your mod_pagespeed:

                ModPagespeedDownstreamCachePurgeLocationPrefix http://localhost:80/
                ModPagespeedDownstreamCachePurgeMethod PURGE
                ModPagespeedDownstreamCacheRewrittenPercentageThreshold 95

2. Use a tool to look at incoming HTTP requests look for PURGE requests. If you 
use varnish you can type:

                varnishlog -m  RxRequest:PURGE                

3. Navigate to www.example.com/somepage.html
4. Look at your logs and look at the URL to which the PURGE request was sent

What is the expected output? What do you see instead?

I would like to see /somepage.html

What I see instead is I would like to see //somepage.html (note the double 
slash)

What version of the product are you using (please check X-Mod-Pagespeed
header)?

1.6.29.7-3566

On what operating system?

Debian 7.0

Which version of Apache?

Apache/2.2.22

Original issue reported on code.google.com by hug...@betabrand.com on 2 Apr 2014 at 12:13