Try to remove assumption that zone's root vnode is marked VROOT

*** 956,966 ****
                  /*
                   * If dotdotting at the root of a filesystem, then
                   * need to traverse back to the mounted-on filesystem
                   * and do the dotdot lookup there.
                   */
!                 if (cs->vp->v_flag & VROOT) {
  
                          /*
                           * If at the system root, then can
                           * go up no further.
                           */
--- 956,966 ----
                  /*
                   * If dotdotting at the root of a filesystem, then
                   * need to traverse back to the mounted-on filesystem
                   * and do the dotdot lookup there.
                   */
!                 if ((cs->vp->v_flag & VROOT) || VN_IS_CURZONEROOT(cs->vp)) {
  
                          /*
                           * If at the system root, then can
                           * go up no further.
                           */
*** 2703,2713 ****
                  /*
                   * If dotdotting at the root of a filesystem, then
                   * need to traverse back to the mounted-on filesystem
                   * and do the dotdot lookup there.
                   */
!                 if (cs->vp->v_flag & VROOT) {
  
                          /*
                           * If at the system root, then can
                           * go up no further.
                           */
--- 2703,2713 ----
                  /*
                   * If dotdotting at the root of a filesystem, then
                   * need to traverse back to the mounted-on filesystem
                   * and do the dotdot lookup there.
                   */
!                 if ((cs->vp->v_flag & VROOT) || VN_IS_CURZONEROOT(cs->vp)) {
  
                          /*
                           * If at the system root, then can
                           * go up no further.
                           */