staging: lustre: ptlrpc: skip lock if export failed

staging: lustre: ptlrpc: skip lock if export failed

This patch resolves IO vs eviction race.
After eviction failed export stayed at stale list,
a client had IO processing and reconnected during it.
A client sent brw rpc with last lock cookie and new connection.
The lock with failed export was found and assert was happened.
 (ost_handler.c:1812:ost_prolong_lock_one())
  ASSERTION( lock->l_export == opd->opd_exp ) failed:

 1. Skip the lock at ldlm_handle2lock if lock export failed.
 2. Validation of lock for IO was added at hpreq_check(). The lock
    searching is based on granted interval tree. If server doesn`t
    have a valid lock, it reply to client with ESTALE.

Signed-off-by: Alexander Boyko <alexander.boyko@seagate.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-7702
Seagate-bug-id: MRP-2787
Reviewed-on: http://review.whamcloud.com/18120
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Vitaly Fertman <vitaly.fertman@seagate.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>