[SCSI] libfc: fix exchange being deleted when the abort itself is timed out

Should not continue when the abort itself is being timeout since in that case
the exchange will be deleted and relesased. We still want to call the
associated response handler to let the layer, e.g., fcp, know the exchange
itself is being timed out.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>