block: urgent request: Update dispatch_urgent in case of requeue/reinsert

The block layer implements a mechanism for verifying that the device
driver won't be notified of an URGENT request if there is already an
URGENT request in flight. This is due to the fact that interrupting an
URGENT request isn't efficient.
This patch fixes the above described mechanism in case the URGENT request
was returned back to the block layer from some reason: by requeue or
reinsert.

CRs-fixed: 473376, 473036, 471736
Change-Id: Ie8b8208230a302d4526068531616984825f1050d
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
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.

Change-Id: I4fb588823f1b2949160cbd3907f4729767932e12
CRs-fixed: 471736
CRs-fixed: 473036
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: Remove "requeuing urgent req" error messages

It is possible for URGENT request to be requeued/reinserted if it was
fetched during the creation of a packed list. This end case is rare and is
not handled at the moment.
This patch changes the messages notifying of the above to debug level
(instead of error) in order to clear the dmesg log.

Change-Id: Ie8bc067e61559a6f702077b95c5dbcc426404232
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>