Prevent payload creation with duplicate uuids

lib/msf/core/db_manager/payload.rb

@@ -1,6 +1,12 @@
 module Msf::DBManager::Payload
 
   def create_payload(opts)
+    if opts[:uuid] && !opts[:uuid].to_s.empty?
+      if Mdm::Payload.find_by(uuid: opts[:uuid])
+        raise ArgumentError.new("A payload with this uuid already exists.") if opts[:ids].nil?
+      end
+    end
+
     Mdm::Payload.create(opts)
   end