The roster set requests are not sent after a session is recovered

[jlemangarin]

Hello !

Please have a look at this JSXC issue and the discussions : https://github.com/jsxc/jsxc/issues/794

When a session is still opened but not polled by any client, the requests are queued in case we re attach the session.

It works well for the presence requests, when the polling restart, Ejabberd send all the pending presence requests to the client.

But it seems not to work for the roster requests as described in the JSXC issue.

Thanks in advance !