Throw our stream of async_pendings through a hash ring; if the virtual
bucket gets hot just start leaving the updates on the floor and move on.
It's off by default; and if you use it you're probably going to leave a
bunch of async updates pointed at a small set of containers in the queue
for the next sweep every sweep (so maybe turn it off at some point)
Co-Authored-By: Alistair Coles <alistairncoles@gmail.com>
Change-Id: Idef25cd6026b02c1b5c10a9816c8c6cbe505e7ed
de88862981