fix plugin test (#7436)

* fix plugin test

* ugh. global state

* Fix plugin test

* Fix TestDeleteChannel

* Remove plugin config listener when shutting down

app/app.go

@@ -11,8 +11,9 @@ import (
 )
 
 type App struct {
-	Srv       *Server
-	PluginEnv *pluginenv.Environment
+	Srv                    *Server
+	PluginEnv              *pluginenv.Environment
+	PluginConfigListenerId string
 }
 
 var globalApp App