Queue: Make WorkerPools and Queues flushable (#10001)

* Make WorkerPools and Queues flushable

Adds Flush methods to Queues and the WorkerPool
Further abstracts the WorkerPool
Adds a final step to Flush the queues in the defer from PrintCurrentTest
Fixes an issue with Settings inheritance in queues

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Change to for loop

* Add IsEmpty and begin just making the queues composed WorkerPools

* subsume workerpool into the queues and create a flushable interface

* Add manager command

* Move flushall to queue.Manager and add to testlogger

* As per @guillep2k

* as per @guillep2k

* Just make queues all implement flushable and clean up the wrapped queue flushes

* cope with no timeout

Co-authored-by: Lauris BH <lauris@nix.lv>

routers/private/manager_unix.go

@@ -0,0 +1,28 @@
+// +build !windows
+
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package private
+
+import (
+	"net/http"
+
+	"code.gitea.io/gitea/modules/graceful"
+
+	"gitea.com/macaron/macaron"
+)
+
+// Restart causes the server to perform a graceful restart
+func Restart(ctx *macaron.Context) {
+	graceful.GetManager().DoGracefulRestart()
+	ctx.PlainText(http.StatusOK, []byte("success"))
+
+}
+
+// Shutdown causes the server to perform a graceful shutdown
+func Shutdown(ctx *macaron.Context) {
+	graceful.GetManager().DoGracefulShutdown()
+	ctx.PlainText(http.StatusOK, []byte("success"))
+}