removeListeners doesn't work as expected for newly created orders, causing callback leak

[ngutman]

Summary

There's an issue causing removeListeners to not remove all the order callbacks that were registered in registerListeners causing a leak, as new orders accumulate this greatly affects performance eventually killing he process

Issue Breakdown

• Upon initial creation of an order with cid the cbGID will be undefined.{cid} since gid was never provided
• Calling registerListeners will register the mentioned cbGID which later is used with removeListeners
• Submitting the order will invoke an update message updating the gid to null (we listen to update to verify the order was successfully submitted
• cbGID will now be null.{cid} mismatching the initial cbGID, rendering removeListeners useless which will increase callbacks size infinitely - this specifically affects systems automatically creating orders.

Sample code

(I took the sample code from https://github.com/bitfinexcom/bfx-api-node-models/#order marking where the issue is prominent)

const { Order } = require('bfx-api-node-models')
const ws = ... // setup WSv2 instance for order updates/submission

// Build new order
const o = new Order({
  cid: Date.now(),
  symbol: 'tBTCUSD',
  price: 7000.0,
  amount: -0.02,
  type: Order.type.EXCHANGE_LIMIT
}, ws) // note WSv2 client passed in here

let closed = false

// Enable automatic updates
o.registerListeners()

o.on('update', () => {
  debug('order updated: %j', o.serialize())
  o.removeListeners() // ISSUE - `cbGID` is not the same as before the `update`
})

o.on('close', () => {
  debug('order closed: %s', o.status)
  closed = true
  o.removeListeners() // Probably also problematic
})

debug('submitting order %d', o.cid)

o.submit().then(() => {
  debug('got submit confirmation for order %d [%d]', o.cid, o.id)
}).catch((err) => {
  debug('failed to submit order: %s', err.message)
})

[pxr64]

Anyway to get around this issue?

[hackable]

removeListeners (apiInterface = this._apiInterface) {
    let cbGID = this.cbGID().replace('null','undefined');
    if (apiInterface) {
      apiInterface.removeListeners(cbGID)
    }
  }

this fixes