Fix yagi AMQP reconnect logic.

Fixes reconnect logic to handle when our rabbit connection drops.
Also, adds ability to periodically close and reopen rabbit connections,
to prevent unack'ed messages from piling up due to rabbit's lack of
support for the amqp commands to requeue messages.
Merge pull request #9 from rackerlabs/rabbit_reconnect

Fix yagi AMQP reconnect logic.