Fix socket read error when websocket upgrade failed

Created by: houfeng0923

WebSocket proxy will throw below exception when target server not ready(target nginx return default http 502 response at current time).

Proxying websocket to /rest/realtime
events.js:298
      throw er; // Unhandled 'error' event
      ^
Error: read ECONNRESET
    at TLSWrap.onStreamRead (internal/stream_base_commons.js:205:27)
Emitted 'error' event on TLSSocket instance at:
    at errorOrDestroy (internal/streams/destroy.js:108:12)
    at TLSSocket.onerror (_stream_readable.js:746:7)
    at TLSSocket.emit (events.js:321:20)
    at emitErrorNT (internal/streams/destroy.js:92:8)
    at emitErrorAndCloseNT (internal/streams/destroy.js:60:3)
    at processTicksAndRejections (internal/process/task_queues.js:84:21) {
  errno: 'ECONNRESET',
  code: 'ECONNRESET',
  syscall: 'read'
}

BTW, If cause by websocket, i think the reason for this is the same as the issue https://github.com/http-party/node-http-proxy/issues/1017 。