Initial working version!!!!! :-D

This version of the mcollective varnish agent is capable of purging
url from varnish cache.

The current implementation is ugly,  it works great!!!

It will use ban.url on varnish 3 servers and purge.url on varnish 2 version.

Currently it could only be used from the rpc call, since there isn't one application
for the client, yet.

To purge the url /images/image.jpg, suposing the domain is example.com
, and the mcollective varnish servers have the puppet class varnish,
use the following command:

mco rpc varnish purge url=http://example.com/images/image.jpg -C varnish

(IMPORTANT: Currently it will purge all entries on cache for /images/image.jpg
it won't respect the hostname. but i want to support that on future versions using
varnish req.http.host == hostname && req.url == uri)