[SCSI] isci: Leave requests alone if already terminating.

Instead of immediately completing any request that has a second
termination call made on it, wait for the TC done/abort HW event.

Signed-off-by: Jeff Skirvin <jeffrey.d.skirvin@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>