The move region function in HMaster only checks whether the region to move exists
It will not return anything if the region is split or in transition which is not movable. So the caller has no way to know if the move region operation is failed.
It is a problem for "region_move.rb". It only gives up moving a region if a exception is thrown.Otherwise, it will wait until a timeout and retry. Without a exception, it have no idea the region is not movable.