Speed up identity update

LCWoT is amazingly fast on bootstrapping, but after that it usually just fetches 1 * sum(own idents) identity update each 30 seconds. These changes should actually make it fetch 10 identity updates each 30 seconds (still not using more than 10 concurrent requests). It is possible to get a backlog larger than 15 as USK edition updates are being added to the backlog as well in which case the sleep time is reduced to 1 second instead of 30 seconds until the backlog is again lower than 15.