db/upnp: move the UPnPDeviceDirectory instance to class UpnpDatabase

Delete the object when closing the database.

src/db/upnp/Discovery.cxx

@@ -275,17 +275,6 @@ UPnPDeviceDirectory::search()
 	return true;
 }
 
-UPnPDeviceDirectory *UPnPDeviceDirectory::getTheDir()
-{
-	// TODO: elimate static variable
-	static UPnPDeviceDirectory *theDevDir;
-	if (theDevDir == nullptr)
-		theDevDir = new UPnPDeviceDirectory();
-	if (theDevDir && !theDevDir->ok())
-		return 0;
-	return theDevDir;
-}
-
 bool
 UPnPDeviceDirectory::getDirServices(std::vector<ContentDirectoryService> &out)
 {

src/db/upnp/Discovery.hxx

@@ -46,14 +46,12 @@ class UPnPDeviceDirectory {
 
 	time_t m_lastSearch;
 
-	UPnPDeviceDirectory();
 public:
+	UPnPDeviceDirectory();
+
 	UPnPDeviceDirectory(const UPnPDeviceDirectory &) = delete;
 	UPnPDeviceDirectory& operator=(const UPnPDeviceDirectory &) = delete;
 
-	/** This class is a singleton. Get the instance here */
-	static UPnPDeviceDirectory *getTheDir();
-
 	/** Retrieve the directory services currently seen on the network */
 	bool getDirServices(std::vector<ContentDirectoryService> &);