Support auto recovery of internet connection error

[chunfuchen]

What is the expected behavior?

For the iterative algorithm, like VQE, it submits the circuits to the backend multiple times; however, sometimes the local machine might lose internet connection or other reasons, and then the program is crashed.
This leads all intermediate results gone.

One aspect to resolve this issue is having a robust querying for the result from the backend.
Another one is generating the checkpoint for the iterative algorithm, and then users can resume that later.

I would like to work on the first one.

[chunfuchen]

#118 solved the problem of internet error.

saving the checkpoint is working progress.

[chunfuchen]

some bug when comparing the status by String, using JobStatus Enum is better.

https://github.com/Qiskit/aqua/blob/master/qiskit_aqua/utils/run_circuits.py#L179

[chunfuchen]

Use terra API to check the status of result now.

[chunfuchen]

Still need to figure out a way to create the snapshot; however for scipy optimizer, it seems that we can not get the internal state during the optimization.

[chunfuchen]

closed and discuss #677