templates/vhost/_proxy.erb misconfigures ProxyPassReverse

See here:
http://httpd.apache.org/docs/2.2/mod/mod_proxy.html#proxypassreverse

When enclosing ProxyPassReverse in a <Location> directive, you drop the
*first* argument, as it will be taken from the enclosing Location. The
second argument is the URL to which we are attempting to proxy.

Very simple change. Tested in my environment, works.