The conversion to blk_delay_queue() missed parts of IDE.
Add a blk_delay_queue() to ensure that the request handler
gets reinvoked when it needs to.

Note that in all but one place the old plug re-run delay of
3 msecs is used, even though it probably could be shorter
for performance reasons in some of those cases.
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>