fix: set correctly request->session

The session cookie was not created because request->session pointed at
a temporary session.

While here:
- do some cleaning in App
- set request->mount too
- add fcgi_cannot_create_request_delay to the config
- fix: in mailregister plugin get model_connector from env (and not from the request)

winixd/core/app.h

@@ -76,10 +76,9 @@ public:
 	Log & GetMainLog();
 	bool InitializePlugins();
 	bool Init();
-	bool InitializeRequestForFastCGI();
-	void SetRequestDependency();
-	void InitializeNewRequest();
-	void PrepareRequest();
+	bool InitializeRequestForFastCGI(Request & request);
+	void SetRequestDependency(Request & request);
+	void InitializeNewRequest(Request & request);
 	void PutRequestToJob();
 	void Start();
 	void Close();