libsas: sas_rediscover_dev did not look at the SMP exec status.

libsas: sas_rediscover_dev did not look at the SMP exec status.

The discovery function "sas_rediscover_dev" had two bugs: 1) it did
not pay attention to the return status from the SMP task execution;
2) the stack variable used for the returned SAS address was compared
against 0 without being initialized.

Signed-off-by: Jeff Skirvin <jeffrey.d.skirvin@intel.com>
[djbw: todo sanitize smp_execute_task return values (see: residue)]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>