Do not require server restart when enabling/disabling plugins (#7592)

app/plugins.go

@@ -394,12 +394,14 @@ func (a *App) RemovePlugin(id string) *model.AppError {
 }
 
 func (a *App) InitPlugins(pluginPath, webappPath string) {
-	a.InitBuiltInPlugins()
-
 	if !utils.IsLicensed() || !*utils.License().Features.FutureFeatures || !*utils.Cfg.PluginSettings.Enable {
 		return
 	}
 
+	if a.PluginEnv != nil {
+		return
+	}
+
 	l4g.Info("Starting up plugins")
 
 	err := os.Mkdir(pluginPath, 0744)
@@ -485,9 +487,13 @@ func (a *App) ShutDownPlugins() {
 	if a.PluginEnv == nil {
 		return
 	}
+
+	l4g.Info("Shutting down plugins")
+
 	for _, err := range a.PluginEnv.Shutdown() {
 		l4g.Error(err.Error())
 	}
 	utils.RemoveConfigListener(a.PluginConfigListenerId)
 	a.PluginConfigListenerId = ""
+	a.PluginEnv = nil
 }