osdblk: Adjust queue limits to lower device's limits

call blk_queue_stack_limits() to copy queue limits from
the underline osd scsi_device. This is absolutely needed
because osdblk cannot sleep when allocating a lower-request and
therefore cannot be bouncing.

TODO: Dynamic changes of limits to the lower device queue
will not reflect in the upper driver

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>