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.
Update rspec definitions for the ProxyPassReverse location fix.