Restore Graceful Restarting & Socket Activation (#7274)

* Prevent deadlock in indexer initialisation during graceful restart

* Move from gracehttp to our own service to add graceful ssh

* Add timeout for start of indexers and make hammer time configurable

* Fix issue with re-initialization in indexer during tests

* move the code to detect use of closed to graceful

* Handle logs gracefully - add a pid suffix just before restart

* Move to using a cond and a holder for indexers

* use time.Since

* Add some comments and attribution

* update modules.txt

* Use zero to disable timeout

* Move RestartProcess to its own file

* Add cleanup routine

modules/ssh/ssh.go

@@ -183,12 +183,7 @@ func Listen(host string, port int, ciphers []string, keyExchanges []string, macs
 		log.Error("Failed to set Host Key. %s", err)
 	}
 
-	go func() {
-		err := srv.ListenAndServe()
-		if err != nil {
-			log.Error("Failed to serve with builtin SSH server. %s", err)
-		}
-	}()
+	go listen(&srv)
 
 }