Open Stack

This patch provides a decent baseline approach for guaranteeing
FIFO for a single producer, while sidestepping race conditions
that could result in observers missing one or more messages.

https://review.openstack.org/#/c/32181

Many thanks to all the fine folks who contributed their ideas,
time, and expertise to help uncover a viable solution.

Please take a look and share your thoughts via Gerrit and/or
#openstack-marconi. I have a hunch this one will take some time
to vet. :D

Cheers,

Kurt | @kgriffs