Send nfs_export_t to untraverse()

*** 1318,1328 ****
           */
          if ((vp->v_flag & VROOT) || VN_IS_CURZONEROOT(vp)) {
  
                  /* extra hold for vp since untraverse might rele */
                  VN_HOLD(vp);
!                 stubvp = untraverse(vp);
  
                  /*
                   * If vp/stubvp are same, we must be at system-or-zone
                   * root because untraverse returned same vp
                   * for a VROOT object.  sarg->vap was setup
--- 1318,1328 ----
           */
          if ((vp->v_flag & VROOT) || VN_IS_CURZONEROOT(vp)) {
  
                  /* extra hold for vp since untraverse might rele */
                  VN_HOLD(vp);
!                 stubvp = untraverse(nfs_get_export(), vp);
  
                  /*
                   * If vp/stubvp are same, we must be at system-or-zone
                   * root because untraverse returned same vp
                   * for a VROOT object.  sarg->vap was setup