pubnub object is leaked on node destroy

[aditanase]

If you create a node-red node of type pubnub, deploy the flow, delete the node, then re-deploy, the old pubnub object is still around receiving messages.

I suspect you should look into the nodes lifecycle and destroy/stop the existing pubnub instance (pn_obj) on the node close event.

See here for an example: https://github.com/node-red/node-red/blob/master/nodes/core/io/10-mqtt.js#L66-L70

If you take pull requests, I'm happy to submit a patch.