Payload generation bug and a few other fixes

* src/core/deployer.py
  -- Instead of burdening the deployer with verifying the existence
  of the payload, we verify it here before doing anything else.
* src/module/generate_payload.py
  -- This was goofing up with JSP payloads
* src/module/invoke_payload.py
  -- Support JSP payload invokes
  -- If we deployed via the ejb or jmx invoker servlets, then the
  path will include a random integer.  We now take care of that
  here.