When the driver is unloading, the nvme transport could be in the process
of submitting new requests, will send abort requests to terminate
associations, or may make LS-related requests.  The driver's abort and
request entry points currently is ignorant of the unloading state and is
starting the requests even though the infrastructure to complete them
continues to teardown.

Change the entry points for new requests to check whether unloading and
if so, reject the requests. Abort routines check unloading, and if so,
noop the request. An abort is noop'd as the teardown paths are already
aborting/terminating the io outstanding at the time the teardown
initiated.
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>