lpfc: Fix to drop PLOGIs from fabric node till LOGO processing completes

The domain controller PLOGI's concurrent with prior LOGO's/unreg_rpi's
completing created a race condition where driver rpi ref count can
inadvertantly hit 0 and the rpi attempted to be freed. This error
sometimes resulted in Warning messages indicating kref.h via
lfpc_nlp_get+0x128.

Correct by dropping any new PLOGI until the prior nport state has settled.

Signed-off-by: Dick Kennedy <dick.kennedy@avagotech.com>
Signed-off-by: James Smart <james.smart@avagotech.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

drivers/scsi/lpfc/lpfc_sli.c

@@ -2249,7 +2249,7 @@ lpfc_sli4_unreg_rpi_cmpl_clr(struct lpfc_hba *phba, LPFC_MBOXQ_t *pmb)
 						 vport->vpi, ndlp->nlp_rpi,
 						 ndlp->nlp_DID,
 						 ndlp->nlp_usg_map, ndlp);
-
+				ndlp->nlp_flag &= ~NLP_LOGO_ACC;
 				lpfc_nlp_put(ndlp);
 			}
 		}