[SCSI] scsi_transport_fc: fc_user_scan correction

Way back when, when the fc_user_scan routine was created, it kept some
of its original logic that walked the rport list and kicked off a scan.
Unfortunately, it didn't keep any of the locking around the rport list,
nor did it consider the synchronous nature of the scan invoked. The result,
there are some scan requests where the rport list changes, thus a subsequent
scan is called on a bogus rport structure and the system NMI's.

Signed-off-by: James Smart <james.smart@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>