block: urgent: Fix dispatching of URGENT mechanism

There are cases when blk_peek_request is called not from blk_fetch_request thus the URGENT request may be started but the flag q->dispatched_urgent is not updated.
block: urgent: Fix dispatching of URGENT mechanism

There are cases when blk_peek_request is called not from blk_fetch_request thus the URGENT request may be started but the flag q->dispatched_urgent is not updated.