scsi: cleanup setting task state in scsi_error_handler()

scsi: cleanup setting task state in scsi_error_handler()

Reading scsi_error_handler() one could easily come away with the
impression that it does its wakeup event check while the task state is
TASK_RUNNING.  In fact it sets TASK_INTERRUPTIBLE at the bottom of the
loop, but that is ~50 lines down.

Just set TASK_INTERRUPTIBLE at the top of loop and be done.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>