I'm not sure if I want to keep this, but it is currently useful for
testing purposes.
The previous logic was to skip opening an SMTP connection in a
newly constructed Dispatcher if no messages were immediately
available in the ready queue.
This logic makes a lot of sense in a multi-node deployment
with shared throttles, so that other nodes have an opportunity
to open connections to drain their own queues, but when testing
a single node it leaves some throughput on the table.
This boolean option allows selecting whether we aggressively
continue to open an SMTP connection even if we may not have
a message ready to send yet, or, if left at the default `false`
value, continue with the original more conservative logic.
Wez Furlong
2fbd9d4c4c