Add retry mechanism

[1204552371]

When the gateway proxy proxy sends a request error, there should be a retry mechanism. The same is true for forwarding including load balancing.
In this way, error 502 caused by socket hang up and connect ECONNREFUSED can be avoided.

maxAutoRetries can be configured in gateway.config.yml. The default is 1.
such as:

      - proxy:
          - action:
              serviceEndpoint: lbsmart
              maxAutoRetries: 1
              changeOrigin: true