nvmet: Disable keep-alive timer when kato is cleared to 0h

[ Upstream commit 0d3b6a8d213a30387b5104b2fb25376d18636f23 ]

Based on nvme spec, when keep alive timeout is set to zero
the keep-alive timer should be disabled.

Signed-off-by: Amit Engel <amit.engel@dell.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>