Publications are GC'd and never re-opened

[lbradstreet]

Seeing this in jepsen. I've made the idle gc timeout very high to work around this for now, however it may just be due to #500.

When testing, may want to make a particular jepsen test that is very bursty to ensure writes are only every minute or so, and the peer link gc timeout very low, so that publications will be closed and re-opened frequently.

[lbradstreet]

I think this may just be a starvation issue. Onyx should probably handle this better though. Maybe we need to push the heartbeats through aeron?

[lbradstreet]

Tested publication GC by staggering messages in jepsen, and it all looks good, so I'm closing this.