[MM-16620] Properly handle analytics client life cycle

Properly handle analytics client life cycle

This change improves the life cycle management of the analytics
client. It does so in two primary ways:
 - Move the client from being a shared pointer to belonging to the
   Server struct.
 - Expose the client.Close() method for proper shutdown of the
   client.

app/diagnostics.go

@@ -58,15 +58,13 @@ const (
 	TRACK_PLUGINS  = "plugins"
 )
 
-var client *analytics.Client
-
 func (a *App) SendDailyDiagnostics() {
 	a.sendDailyDiagnostics(false)
 }
 
 func (a *App) sendDailyDiagnostics(override bool) {
 	if *a.Config().LogSettings.EnableDiagnostics && a.IsLeader() && (!strings.Contains(SEGMENT_KEY, "placeholder") || override) {
-		a.initDiagnostics("")
+		a.Srv.initDiagnostics("")
 		a.trackActivity()
 		a.trackConfig()
 		a.trackLicense()
@@ -76,24 +74,8 @@ func (a *App) sendDailyDiagnostics(override bool) {
 	}
 }
 
-func (a *App) initDiagnostics(endpoint string) {
-	if client == nil {
-		client = analytics.New(SEGMENT_KEY)
-		client.Logger = a.Log.StdLog(mlog.String("source", "segment"))
-		// For testing
-		if endpoint != "" {
-			client.Endpoint = endpoint
-			client.Verbose = true
-			client.Size = 1
-		}
-		client.Identify(&analytics.Identify{
-			UserId: a.DiagnosticId(),
-		})
-	}
-}
-
 func (a *App) SendDiagnostic(event string, properties map[string]interface{}) {
-	client.Track(&analytics.Track{
+	a.Srv.diagnosticClient.Track(&analytics.Track{
 		Event:      event,
 		UserId:     a.DiagnosticId(),
 		Properties: properties,