Rudder

My case: upgrade my Rudder, jetty restarts, he found new system techniques, update tech library, and start a new promise generation update. Ok, but during the promise generation jetty restarted (don't know why but it did) ;
so jetty starts ... and it's ok for him, do not need to start a promise generation and I keep my old broken promises :(

Add a flag file when we start a promise generation, and look for that flag at startup so we can launch a generation if jetty restarted during the previous one

Don't forget to wipe that file after the end of a promise generation!