MRP-1944 ldlm: ldlm_process_extent_lock()) ASSERTION failed

ASSERTION( lock->l_granted_mode != lock->l_req_mode ) is failing
when resending LDLM_FL_REPLAY with LDLM_FL_BLOCK_WAIT.

Don't add lock to waiting list as it is already added or granted.

Change-Id: Ib8e5d2c7588f6cacd1723529e70d29f63742caad
Signed-off-by: Andriy Skulysh <Andriy_Skulysh@xyratex.com>
Reviewed-by: Vitaly Fertman <vitaly_fertman@xyratex.com>
Reviewed-by: Alexander Boyko <alexander_boyko@xyratex.com>