Test that reconnect doesn't drop partially sent messages

[caleblloyd]

Add a test that checks that client-side reconnects don't drop partially sent messages out of the send buffer

[caleblloyd]

Interesting - got a dropped message in this test run

[mtmk]

LGTM

[mtmk]

Interesting - got a dropped message in this test run

I'm also getting it sometimes locally:

Expected: 1278
Actual:   1274

Also copied it to a 2.0.x codebase, fails with 0 actual!

Edit: the new branch is a bit better:

Expected: 5298
Actual:   5252

[caleblloyd]

I'm also getting it sometimes locally

Do you think we should put a range in then, to prevent it from being a flapper? With an Issue to follow-up on it?

[mtmk]

I'm also getting it sometimes locally

Do you think we should put a range in then, to prevent it from being a flapper? With an Issue to follow-up on it?

I think that's reasonable. Feel free to merge when you're happy with it.

[caleblloyd]

Great, I've adapted the test to check for <= 1% loss. added my theory as to why there may be loss in the comments:

        // some messages may still be lost, as socket could have been disconnected
        // after socket.WriteAsync returned, but before OS sent
        // check to ensure that the loss was < 1%

If that is indeed where the loss is occurring, I think it is acceptable. Because this loss would occur anyways if we didn't do any buffering at all.