Land rapid7#6117, Fix nil http_method in php_include

Author: kgray-r7

modules/exploits/unix/webapp/php_include.rb

@@ -121,6 +121,7 @@ def php_exploit
       end
       uris.uniq!
       print_status("Loaded #{uris.length} URLs")
+      http_method = "GET"
     end
 
     # Very short timeout because the request may never return if we're