Execution example::

  logical_table_remove \
    --logical_table Logs \
    --shard_key timestamp
  # [
  #   [
  #     -55, 
  #     1337566253.89858, 
  #     0.000355720520019531, 
  #     "object corrupt: <[column][remove][index] hook has a dangling reference: <Logs_20160320.timestamp> -> <Timestamps.logs_20160320_", 
  #     [
  #       [
  #         "Groonga::Sharding::LogicalTableRemoveCommand.remove_table", 
  #         "/home/kou/work/c/groonga.clean/plugins/sharding/logical_table_remove.rb", 
  #         156
  #       ]
  #     ]
  #   ]
  # ]
