Make sure stageless is supported

Author: OJ

lib/msf/core/payload/python/meterpreter_loader.rb

@@ -98,14 +98,15 @@ def stage_meterpreter(opts={})
     # The callback URL can be different to the one that we're receiving from the interface
     # so we need to generate it
     # TODO: move this to somewhere more common so that it can be used across payload types
+    uri = "/#{(opts[:uri].to_s == '' ? opts[:url] : opts[:uri].to_s).split('/').reject(&:empty?)[-1]}"
     callback_url = [
       opts[:url].split(':')[0],
       '://',
       (ds['OverrideRequestHost'] == true ? ds['OverrideRequestLHOST'] : ds['LHOST']).to_s,
       ':',
       (ds['OverrideRequestHost'] == true ? ds['OverrideRequestLPORT'] : ds['LPORT']).to_s,
       ds['LURI'].to_s,
-      opts[:uri].to_s,
+      uri,
       '/'
     ].join('')