Updates to /status API

This patch returns additional data from the /status API call. Specifically, it
returns a worker list, the message broker connection status, the database
connection status, and the Pulp version (RHBZ #704184).

There is a small behavior change to include the resource manager and scheduler
as part of the worker heartbeat list. Previously, these were not included in
the list.
Since none of the methods in this class use self, and since there is no state, could we just make everything in this module just be functions? That would be much more Pythonic and simpler too (since you wouldn't need to instantiate anything to call these functions.