When searching in the db for a feed with a url similar to a passed url, first make sure that the passed url has a valid uri-scheme. If it has no valid uri-scheme, it defaults to http://

This makes sense because feeds saved in the db are guaranteed to have an http or https uri-scheme. If e.g. we search for 'xkcd.com', we want to find the feed already in the db with url 'http://xkcd.com'