NEX-1142 move rwlock to vdev to protect vdev_tsd
not just ldi handle.
This way we serialize open/close, yet allow parallel I/O.
NEX-1065 Added serialization to avoid race
between ldi notification and I/O path.
Also fixes OS-124, NEX-1051, NEX-1062.

*** 20,30 ****
   */
  /*
   * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   * Copyright (c) 2013 Joyent, Inc. All rights reserved.
!  * Copyright 2012 Nexenta Systems, Inc.  All rights reserved.
   */
  
  #ifndef _SYS_VDEV_DISK_H
  #define _SYS_VDEV_DISK_H
  
--- 20,30 ----
   */
  /*
   * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   * Copyright (c) 2013 Joyent, Inc. All rights reserved.
!  * Copyright 2014 Nexenta Systems, Inc.  All rights reserved.
   */
  
  #ifndef _SYS_VDEV_DISK_H
  #define _SYS_VDEV_DISK_H
  
*** 44,54 ****
  typedef struct vdev_disk {
          ddi_devid_t     vd_devid;
          char            *vd_minor;
          ldi_handle_t    vd_lh;
          list_t          vd_ldi_cbs;
-         boolean_t       vd_ldi_offline;
  } vdev_disk_t;
  #endif
  
  extern int vdev_disk_physio(vdev_t *,
      caddr_t, size_t, uint64_t, int, boolean_t);
--- 44,53 ----