Use PAYLOAD instead of CMD

Author: jvazquez-r7

modules/exploits/linux/http/vap2500_tools_command_exec.rb

@@ -79,7 +79,7 @@ def exploit
 
     print_status("#{peer} - Exploiting...")
 
-    if datastore['CMD']
+    if datastore['PAYLOAD'] == 'cmd/unix/generic'
       exploit_cmd
     else
       exploit_session