non-blocking active FTP: cleanup multi state usage

Backpedaled out the funny double-change of state in the multi state
machine by adding a new argument to the do_more() function to signal
completion. This way it can remain in the DO_MORE state properly until
done. Long term, the entire DO_MORE logic should be moved into the FTP
code and be hidden from the multi code as the logic is only used for
FTP.