Removed autosharing of all disk drives during redirect of any drive.

According to issue #1843 we shouldn't redirect all disk drives every time when we redirected one drive. 
This flag settings->RedirectDrives means that we will redirect root as media (All drives), so I don't think that it is correct to enable it each time we added redirection of specific drive.
settings->RedirectDrives should be set to TRUE only when +drives option is specified.
Please, correct me if I'm wrong.