PLT-6080 moving clustering to memberlist (#6499)

* PLT-6080 adding cluster discovery service

* Adding memberlist lib

* Adding memberlist lib

* WIP

* WIP

* WIP

* WIP

* Rolling back config changes

* Fixing make file

* Fixing config for cluster

* WIP

* Fixing system console for clustering

* Fixing default config

* Fixing config

* Fixing system console for clustering

* Tweaking hub setting

* Bumping up time

* merging vendor dir

* Updating vendor dir

* Fixing unit test

* Fixing bad merge

* Remove some testing code

* Moving comment

* PLT-6868 adding db ping retry

* Removing unused loc strings

* Adding defer to cancel

app/cluster_discovery_test.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package app
+
+import (
+	"testing"
+
+	"time"
+
+	"github.com/mattermost/platform/model"
+)
+
+func TestClusterDiscoveryService(t *testing.T) {
+	Setup()
+
+	ds := NewClusterDiscoveryService()
+	ds.Type = model.CDS_TYPE_APP
+	ds.ClusterName = "ClusterA"
+	ds.AutoFillHostname()
+
+	ds.Start()
+	time.Sleep(2 * time.Second)
+
+	ds.Stop()
+	time.Sleep(2 * time.Second)
+}