fix shortest_path when target is found before reaching landmark
fix shortest_path when target is found before reaching landmark

kumagi/jubatus_core,rimms/jubatus_core,Asuka52/jubatus,jubatus/jubatus,elkingtonmcb/jubatus,rimms/jubatus_core,rimms/jubatus,gintenlabo/jubatus_core,kmaehashi/jubatus_core,jubatus/jubatus,kumagi/jubatus_core,kumagi/jubatus_core,gintenlabo/jubatus,kmaehashi/jubatus_core,gintenlabo/jubatus_core,elkingtonmcb/jubatus,gintenlabo/jubatus_core,Asuka52/jubatus,rimms/jubatus_core,kmaehashi/jubatus,kmaehashi/jubatus_core,kmaehashi/jubatus_core,gintenlabo/jubatus,kumagi/jubatus_core,rimms/jubatus,mathn/jubatus,kmaehashi/jubatus,gintenlabo/jubatus_core,roselleebarle04/jubatus,jubatus/jubatus,rimms/jubatus_core,roselleebarle04/jubatus,mathn/jubatus