[rtorrent] Fixed bug where setting changes would not take effect

Discovered an issue where adjustments to rtorrent downloader settings wouldn't take effect until you restart the CouchPotato server.

This is a result of of how ```connect()``` on first command/request creates a persistent ```RTorrent``` object based on the current settings and is used for all future calls.

Not sure what you think of the changes in ```couchpotato/core/settings/__init__.py```, let me know if there is a better way this could be done.

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**Note:** It looks like the Deluge downloader might have this same issue as well, I suspect this will need updating in a similar way to this PR.