MRP-2261 flock: Don't merge unprocessed flock locks

An unprocessed lock can be destroyed in race between
ldlm_lock_enqueue() and ldlm_process_flock_lock()

Change-Id: I2c0a9c4ab4bf00540f1c64894f3f0816385b2cec
Signed-off-by: Andriy Skulysh <andriy.skulysh@seagate.com>
Reviewed-on: http://es-gerrit.xyus.xyratex.com:8080/4465
Tested-by: Jenkins
Reviewed-by: Alexander Boyko <alexander.boyko@seagate.com>
Tested-by: Alexander Lezhoev <alexander.lezhoev@seagate.com>
Reviewed-by: Vitaly Fertman <vitaly.fertman@seagate.com>