Determine and implement the behavior of dcurl with different remote component status

[marktwtn]

dcurl should keep working well with the different status of the remote component behind the remote interface, such as inactivation, termination or restart of RabbitMQ broker and remote worker .

• Termination: It is initialized successfully and runs for a while but somehow been closed.
• Inactivation: It is never been run, which is treated as initialization failure.

RabbitMQ broker	Remote worker	Determined behavior
Inactivation Termination	*	Use local available hardware to do the PoW Print out the warning
Restart	*	Use remote worker to do the PoW
Normal	Inactivation Termination	Wait remote worker for a while(10 sec) and use local available hardware to do the PoW if it does not restart
Normal	Restart Normal	Use remote worker to do the PoW