LU-5579 ldlm: re-sent enqueue vs lock destroy race

LU-5579 ldlm: re-sent enqueue vs lock destroy race

Upon lock enqueue re-send, lock is pinned by ldlm_handle_enqueue0,
however it may race with client eviction or even lock cancel (if
a reply for the original RPC finally reached the client) and the
lock cannot be found by cookie anymore:

ASSERTION( lock != NULL ) failed: Invalid lock handle

Signed-off-by: Vitaly Fertman <vitaly_fertman@xyratex.com>
Change-Id: I9d8156bf78a1b83ac22ffaa1148feb43bef37b1a
Xyratex-bug-id: MRP-2094
Reviewed-on: http://review.whamcloud.com/11839
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>