lib/client: remove unused connect event

As pointed out by @Qard, it's not used.  Remove it.
test: shorten test duration

Make the 'should not lose messages while disconnected' test run quicker.
Before, it took ~800 ms to complete.  Now it finishes in ~300 ms.

Coincidentally, this change seems to make the intermittent test failure
trigger more reliably.  To be addressed in a follow-up commit.