isci: Make sure all TCs are terminated and cleaned in LUN reset.

In the libsas error path, SATA disks require extra handling in
libata to recover operation.  However, libsas expects to be able
to immediately recover all outstanding I/O once the error handler
escalation stops.  This patch fixes the condition where the libata
error handler is scheduled for operation but libsas has already
deleted the outstanding sas_tasks.

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