Only link delayed transport AFTER real transport has called transportReady()

[zhangkun83]

There is no benefit of creating streams on a transport that has not called transportReady(), because they will be buffered anyway. Besides, transport connection may turn out to be a failure, which will fail the pending streams on it, spamming transient errors to the callers. Those streams, however, if created on a transport that has called transportReady(), would have a higher chance of success.

Proposed change: TransportSet calls setTransport on delayed transport in the transportReady() callback of the real transport.

[ejona86]

In the case that the last transport attempt fails in a TransportSet, it should still result in a failure of the calls, ideally with some error information. That error information can either come from transportShutdown(Status) or by eagerly assigning only the last transport.

[sduskis]

@ejona86 suggested in #1476 that this could be a fix for a problem we're seeing. What's the ETA for this fix?

[zhangkun83]

I will work on #1476 first, then this one. Hopefully they can be done by end of next week.