sw test tool: refactor: Add a class that receives messages
sw test tool: refactor: Move a test state variable to TestPart class

  OfTester.state ->
  TestPart.state

And add getter/setter methods.

  TestPart.get_state()
  TestPart.set_state(state)
sw test tool: refactor: Move a list of transaction ids to TestPart class

  OfTester.send_msg_xids ->
  TestPart.send_msg_xids

And add getter/setter methods.

  TestPart.add_xid(xid)
  TestPart.get_xids()
  TestPart.reset_xids()
sw test tool: refactor: Move a list of received messages to TestPart class

  OfTester.rcv_msgs ->
  TestPart.rcv_msgs

And add getter/setter methods.

  TestPart.add_msg(msg)
  TestPart.get_msgs()
  TestPart.reset_msgs()
sw test tool: refactor: Move a method that waits to receive messages to TestPart class

  OfTester._wait() ->
  TestPart.wait()

And move a variable that is used by the method.

  OfTester.waiter ->
  TestPart.waiter
sw test tool: refactor: Move methods that handle messages to TestPart class

  OfTester.flow_stats_reply_handler(ev) ->
  TestPart.flow_stats_reply_hanlder(ev)

  OfTester.table_stats_reply_hanlder(ev) ->
  TestPart.table_stats_reply_handler(ev)

  OfTester.port_stats_reply_hanlder(ev) ->
  TestPart.port_stats_reply_hanlder(ev)

  OfTester.barrier_reply_handler(ev) ->
  TestPart.barrier_reply_handler(ev)

  OfTester.packet_in_handler(ev) ->
  TestPart.packet_in_handler(ev)

  OfTester.error_msg_handler(ev) ->
  TestPart.error_msg_handler(ev)

And instantiate TestPart class as a context to enable those handlers.
sw test tool: refactor: Remove unnecessary methods

[obsolete]
  TestPart.get_xids()
  TestPart.add_msgs(msg)

[integrated]
  TestPart.reset_xids() and TestPart.reset_msgs() ->
  TestPart.reset()