scsi: target/core: Simplify the LUN RESET implementation

Due to the task management handling rework it is safe to wait for a TMF
that is not in the active state. Hence remove the CMD_T_ACTIVE test from
core_tmr_drain_tmr_list(). Additionally, call __target_check_io_state()
instead of open coding it.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>