fix(bosh): mark first request dead when second is done

[sunduev]

Logic to restart first request if second finishes earlier doesn't work.

strophejs/src/bosh.js

Lines 634 to 642 in 1877ecb

	// if request 1 finished, or request 0 finished and request
	// 1 is over Strophe.SECONDARY_TIMEOUT seconds old, we need to
	// restart the other - both will be in the first spot, as the
	// completed request has been removed from the queue already
	if (reqIs1 ||
	(reqIs0 && this._requests.length > 0 &&
	this._requests[0].age() > Math.floor(Strophe.SECONDARY_TIMEOUT * this.wait))) {
	this._restartRequest(0);
	}

Request is never marked as dead in this case because we remove it on previous step.

strophejs/src/bosh.js

Lines 622 to 628 in 1877ecb

	const valid_request = reqStatus > 0 && reqStatus < 500;
	const too_many_retries = req.sends > this._conn.maxRetries;
	if (valid_request || too_many_retries) {
	// remove from internal queue
	this._removeRequest(req);
	Strophe.debug("request id "+req.id+" should now be removed");
	}

This leads to long timeout instead of possible short secondary timeout in _processRequest

So we should save booleans before request is removed.
It was intended to work this way but did break on commit a7a1413

[jcbrand]

Thanks!