Land rapid7#6370, add joomla reference

Author: lsato-r7

modules/exploits/multi/http/joomla_http_header_rce.rb

@@ -34,6 +34,7 @@ def initialize(info = {})
           ['URL', 'https://blog.sucuri.net/2015/12/joomla-remote-code-execution-the-details.html'],
           ['URL', 'https://blog.sucuri.net/2015/12/remote-command-execution-vulnerability-in-joomla.html'],
           ['URL', 'https://developer.joomla.org/security-centre/630-20151214-core-remote-code-execution-vulnerability.html'],
+          ['URL', 'https://blog.patrolserver.com/2015/12/17/in-depth-analyses-of-the-joomla-0-day-user-agent-exploit/'],
           ['URL', 'https://translate.google.com/translate?hl=en&sl=auto&tl=en&u=http%3A%2F%2Fdrops.wooyun.org%2Fpapers%2F11330'],
           ['URL', 'https://translate.google.com/translate?hl=en&sl=auto&tl=en&u=http%3A%2F%2Fwww.freebuf.com%2Fvuls%2F89754.html'],
           ['URL', 'https://bugs.php.net/bug.php?id=70219']