Make joomla_media_upload_exec more generic

Remove dependency on tmpl=component and allow 302 redirects in addition to 200 responses.

These updates were necessary to successfully exploit a particular instance of Joomla 2.5.7 I encountered, and should be general enough to be applied back to the module.

Pcap of exploit traffic available via email, and potentially URL to this instance for testing. Let me know what you need. Thanks!