Revert exi_zone to exi_zoneid, and install exi_ne backpointer

*** 443,453 ****
                  resp->status = NFS3ERR_ACCES;
                  goto out1;
          }
  
          fhp = &args->what.dir;
!         ASSERT3P(curzone, ==, exi->exi_zone); /* exi is guaranteed non-NULL. */
          if (strcmp(args->what.name, "..") == 0 &&
              EQFID(&exi->exi_fid, FH3TOFIDP(fhp))) {
                  if ((exi->exi_export.ex_flags & EX_NOHIDE) &&
                      ((dvp->v_flag & VROOT) || VN_IS_CURZONEROOT(dvp))) {
                          /*
--- 443,453 ----
                  resp->status = NFS3ERR_ACCES;
                  goto out1;
          }
  
          fhp = &args->what.dir;
!         ASSERT3U(curzone->zone_id, ==, exi->exi_zoneid); /* exi is non-NULL */
          if (strcmp(args->what.name, "..") == 0 &&
              EQFID(&exi->exi_fid, FH3TOFIDP(fhp))) {
                  if ((exi->exi_export.ex_flags & EX_NOHIDE) &&
                      ((dvp->v_flag & VROOT) || VN_IS_CURZONEROOT(dvp))) {
                          /*
*** 1334,1344 ****
          if (vp == NULL) {
                  error = ESTALE;
                  goto err;
          }
  
!         ASSERT3P(curzone, ==, exi->exi_zone); /* exi is guaranteed non-NULL. */
          ns = nfs3_get_srv();
  
          if (is_system_labeled()) {
                  bslabel_t *clabel = req->rq_label;
  
--- 1334,1344 ----
          if (vp == NULL) {
                  error = ESTALE;
                  goto err;
          }
  
!         ASSERT3U(curzone->zone_id, ==, exi->exi_zoneid); /* exi is non-NULL. */
          ns = nfs3_get_srv();
  
          if (is_system_labeled()) {
                  bslabel_t *clabel = req->rq_label;
  
*** 4137,4147 ****
          if (vp == NULL) {
                  error = ESTALE;
                  goto out;
          }
  
!         ASSERT3P(curzone, ==, exi->exi_zone); /* exi is guaranteed non-NULL. */
          ns = nfs3_get_srv();
          bva.va_mask = AT_ALL;
          error = VOP_GETATTR(vp, &bva, 0, cr, NULL);
  
          /*
--- 4137,4147 ----
          if (vp == NULL) {
                  error = ESTALE;
                  goto out;
          }
  
!         ASSERT3U(curzone->zone_id, ==, exi->exi_zoneid); /* exi is non-NULL. */
          ns = nfs3_get_srv();
          bva.va_mask = AT_ALL;
          error = VOP_GETATTR(vp, &bva, 0, cr, NULL);
  
          /*