In swarm mode, deviceShifuBase supports multiple EdgeDevices

[kris21he]

This implementation should come after #538

In the edgedevice.yaml file supports multiple edge device records

1. Multiple edgedevice records can be added into edgedevice.yaml
2. Shifu can reads multiple edgeDevices config into its program

Accept criteria:

1. config multiple edgedevice records in examples/httpDeviceShifu/deployment/http-edgedevice.yaml
2. kubectl apply -f examples/httpDeviceShifu/deployment no error
3. multiple records can read from http-edgedevice.yaml into shifu
4. the API provided by deviceshifu can keep working (eg. multiple devices info should returned compare to the single mode)